PlayByKey Music Theory
NPM · @PLAYBYKEY/THEORY-MCP · SCANNED SEP 23
Chords, scales, progressions, transposition, and MIDI tools for music theory AI agents.
Available components
How this component scores in each security and reliability category. Every signal is checked automatically from public evidence about the published package, including repeated runs of it in an isolated sandbox, and we only credit what we can confirm. How we score → Why this is hard to score →
Supply Chain Security98
- No malware found by supply-chain analysis.Pass
- No known CVEs affecting this package version or its production dependencies.Pass
- No install/post-install scripts declared.Pass
- 31 of 96 dependencies flagged as unhealthy. View diagnostics → Partial
Provenance & Transparency48
- Source repository is publicly reachable at the declared URL. View diagnostics → Pass
- Provenance check failed: no build-provenance attestation is published. See how to fix → View diagnostics → Fail
- Clear OSI-approved license (MIT).Pass
- Actively maintained (last published 8 days ago).Pass
- Publishes a security disclosure policy (SECURITY.md).Pass
Schema Quality & AI Usability74
- AI-judged instruction clarity (good).Pass
- Tool/resource definitions use about 1749 tokens (~54/item across 32 items; 32 tools + 0 resources), lean.Pass
- Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management97
- Stability observed for 29 of 30 days with no destabilising changes; credit accrues until the full window elapses.Partial
Tool Coverage100
- 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
- 100% of tool parameters carry a description.Pass
Tool Safety100
- No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
- We read all 32 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
- An AI judge read all 32 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities100
- Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.Pass
How do I install the PlayByKey Music Theory MCP server?
PlayByKey Music Theory runs locally as an npm package, launched with npx -y @playbykey/theory-mcp. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.
npm · @playbykey/theory-mcp
claude mcp add com-playbykey-theory-mcp -- npx -y @playbykey/theory-mcp
{
"mcpServers": {
"com-playbykey-theory-mcp": {
"command": "npx",
"args": [
"-y",
"@playbykey/theory-mcp"
]
}
}
} {
"servers": {
"com-playbykey-theory-mcp": {
"command": "npx",
"args": [
"-y",
"@playbykey/theory-mcp"
]
}
}
} codex mcp add com-playbykey-theory-mcp -- npx -y @playbykey/theory-mcp
{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"com-playbykey-theory-mcp": {
"type": "local",
"command": [
"npx",
"-y",
"@playbykey/theory-mcp"
],
"enabled": true
}
}
} openclaw mcp add com-playbykey-theory-mcp --command npx --arg -y --arg @playbykey/theory-mcp
mcp_servers:
com-playbykey-theory-mcp:
command: "npx"
args: ["-y", "@playbykey/theory-mcp"] {
"McpServers": {
"com-playbykey-theory-mcp": {
"Transport": "stdio",
"Command": "npx",
"Arguments": [
"-y",
"@playbykey/theory-mcp"
]
}
}
} assistant mcp add com-playbykey-theory-mcp -t stdio -c npx -a -y @playbykey/theory-mcp
{
"mcpServers": {
"com-playbykey-theory-mcp": {
"command": "npx",
"args": [
"-y",
"@playbykey/theory-mcp"
]
}
}
} Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.
- 23 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 93 to 97. That category is still filling its 30-day observation window: 28 days of observed history at the previous scan, 29 at this one. The score rises as the window fills, whether or not the server changes.
- 20 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 83 to 87. That category is still filling its 30-day observation window: 25 days of observed history at the previous scan, 26 at this one. The score rises as the window fills, whether or not the server changes.
- 18 Sept 26 −2
- Stability: pass → 0.80 functional
- 17 Sept 26 0
- Stability: 0.97 → pass security
- 16 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 93 to 97. That category is still filling its 30-day observation window: 28 days of observed history at the previous scan, 29 at this one. The score rises as the window fills, whether or not the server changes.
- 13 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 83 to 87. That category is still filling its 30-day observation window: 25 days of observed history at the previous scan, 26 at this one. The score rises as the window fills, whether or not the server changes.
- 11 Sept 26 −2
- Stability: pass → 0.80 functional
- 10 Sept 26 0
- Stability: 0.97 → pass security
Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.
Captured 23 Sept 2026 · Analysed npm/@playbykey/theory-mcp@1.6.0
Provenance No attestation
The registry publishes no build provenance for this version, so there is nothing to verify.
| Result | No attestation |
|---|---|
| Ecosystem | npm |
Background: How many MCP packages publish verified provenance →
Dependencies 96 packages
| Packages resolved | 96 |
|---|---|
| Stale | 31 |
| Tree resolution | Complete |
Background: SBOMs and build attestations, explained →
The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →
build_note_map ~53
Returns structured per-note data for a scale: note name, scale degree (1-based), and semitone offset from root.
| Name | Type | Req | Description |
|---|---|---|---|
| root | string | yes | Root note |
| scale_type | string | yes | Scale type |
No output schema declared.
No examples provided.
get_available_inversions ~37
Returns the valid inversion numbers for a chord type, based on its note count.
| Name | Type | Req | Description |
|---|---|---|---|
| chord_type | string | yes | Chord type |
No output schema declared.
No examples provided.
get_bebop_scale_notes ~58
Returns the eight notes of a bebop scale variant for a root - a diatonic scale plus one chromatic passing tone.
| Name | Type | Req | Description |
|---|---|---|---|
| root | string | yes | Root note |
| type | string | yes | Bebop scale variant |
No output schema declared.
No examples provided.
get_chord_by_degree ~71
Returns the diatonic chord at a specific scale degree (1-7) for a key/mode.
| Name | Type | Req | Description |
|---|---|---|---|
| degree | integer | yes | Scale degree (1-7) |
| mode | string | – | Mode name (defaults to ionian if omitted) |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_chord_inversion ~68
Reorders a chord's notes so the given inversion's chord tone is lowest.
| Name | Type | Req | Description |
|---|---|---|---|
| chord_type | string | yes | Chord type |
| inversion | integer | yes | Inversion number (0-4, valid range depends on chord type) |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_chord_notes ~43
Returns the notes of a chord given a root and chord type.
| Name | Type | Req | Description |
|---|---|---|---|
| chord_type | string | yes | Chord type |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_circle_of_fifths ~29
Returns all 12 chromatic notes in ascending-fifths order starting from C.
Input schema present but exposes no named parameters.
No output schema declared.
No examples provided.
get_diatonic_chords ~61
Returns the 7 diatonic triads for a key/mode, one per scale degree, in degree order.
| Name | Type | Req | Description |
|---|---|---|---|
| mode | string | – | Mode name (defaults to ionian if omitted) |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_enharmonic_labels ~84
Returns combined sharp/flat display labels for a list of sharp-spelled notes, e.g. ["C#", "D"] -> ["Db/C#", "D"]. Natural notes are unaffected. Input must already be sharp-spelled - use get_sharps first if you have flat-spelled notes.
| Name | Type | Req | Description |
|---|---|---|---|
| notes | array | yes | Sharp-spelled notes to label |
No output schema declared.
No examples provided.
get_flats ~93
Respells a list of sharp-spelled notes as flats, e.g. ["C#", "D"] -> ["Db", "D"]. Natural notes are unaffected. Input must already be sharp-spelled (as returned by get_scale_notes, get_mode_notes, etc.) - use get_sharps first if you have flat-spelled notes.
| Name | Type | Req | Description |
|---|---|---|---|
| notes | array | yes | Sharp-spelled notes to convert to flats |
No output schema declared.
No examples provided.
get_harmonic_minor_mode_notes ~46
Returns the seven notes of a harmonic minor mode for a root.
| Name | Type | Req | Description |
|---|---|---|---|
| mode | string | yes | Harmonic minor mode |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_key_signature ~47
Returns the sharp or flat count for a given key, treated as a major-key tonic (minor-key signatures are not exposed by this tool).
| Name | Type | Req | Description |
|---|---|---|---|
| key | string | yes | Key root note |
No output schema declared.
No examples provided.
get_melodic_minor_mode_notes ~47
Returns the seven notes of a melodic minor mode for a root.
| Name | Type | Req | Description |
|---|---|---|---|
| mode | string | yes | Melodic minor mode |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_melodic_minor_notes ~35
Returns the seven notes of the ascending melodic minor scale for a root.
| Name | Type | Req | Description |
|---|---|---|---|
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_modal_root ~51
Returns the root note of a mode within a given parent (Ionian/major) key.
| Name | Type | Req | Description |
|---|---|---|---|
| mode | string | yes | Mode name |
| parent_key | string | yes | Root of the parent major key |
No output schema declared.
No examples provided.
get_mode_info ~34
Returns display metadata for a mode: name, scale degree, and characteristic description.
| Name | Type | Req | Description |
|---|---|---|---|
| mode | string | yes | Mode name |
No output schema declared.
No examples provided.
get_mode_notes ~44
Returns the 7 notes of a diatonic mode for a given root note.
| Name | Type | Req | Description |
|---|---|---|---|
| mode | string | yes | Mode name |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_parent_scale_modes ~48
Returns all 7 modal rotations of the parent key for a given root and mode.
| Name | Type | Req | Description |
|---|---|---|---|
| mode | string | yes | Mode name |
| root | string | yes | Root note of the mode |
No output schema declared.
No examples provided.
get_progression_in_key ~47
Renders a named catalog progression as chords in a given key, in order.
| Name | Type | Req | Description |
|---|---|---|---|
| progression_id | string | yes | Catalog progression ID |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
get_relative_major ~32
Returns the relative major root for a minor key.
| Name | Type | Req | Description |
|---|---|---|---|
| minor_key | string | yes | Root of the minor key |
No output schema declared.
No examples provided.
get_relative_minor ~32
Returns the relative minor root for a major key.
| Name | Type | Req | Description |
|---|---|---|---|
| major_key | string | yes | Root of the major key |
No output schema declared.
No examples provided.
get_roman_numeral ~64
Returns the roman numeral for a scale degree in a mode - case and suffix reflect diatonic triad quality.
| Name | Type | Req | Description |
|---|---|---|---|
| degree | integer | yes | Scale degree (1-7) |
| mode | string | – | Mode name (defaults to ionian if omitted) |
No output schema declared.
No examples provided.
get_scale_degree ~72
Returns the 1-based scale degree of a note within a root + scale type, or null if the note is not in the scale.
| Name | Type | Req | Description |
|---|---|---|---|
| note | string | yes | Note to locate within the scale |
| root | string | yes | Root note of the scale |
| scale_type | string | yes | Scale type |
No output schema declared.
No examples provided.
get_scale_notes ~69
Returns the notes of a scale by type. Covers all ScaleType values: major, blues, pentatonic-major, pentatonic-minor, harmonic-minor, melodic-minor, chromatic.
| Name | Type | Req | Description |
|---|---|---|---|
| root | string | yes | Root note |
| scale_type | string | yes | Scale type |
No output schema declared.
No examples provided.
get_semitone_distance ~43
Returns the ascending semitone distance between two notes (0-11).
| Name | Type | Req | Description |
|---|---|---|---|
| from | string | yes | Starting note |
| to | string | yes | Target note |
No output schema declared.
No examples provided.
get_sharps ~100
Respells a list of notes to canonical sharp spelling, e.g. ["Db", "C#", "D"] -> ["C#", "C#", "D"]. Most tools accept flat-spelled input directly, but get_flats and get_enharmonic_labels require sharp-spelled input - use this to normalize flat-spelled notes before calling those two.
| Name | Type | Req | Description |
|---|---|---|---|
| notes | array | yes | Notes to normalize to sharps (sharp or flat input accepted) |
No output schema declared.
No examples provided.
is_note_in_scale ~61
Returns true if the given note is present in the specified root + scale type, false otherwise.
| Name | Type | Req | Description |
|---|---|---|---|
| note | string | yes | Note to check |
| root | string | yes | Root note of the scale |
| scale_type | string | yes | Scale type |
No output schema declared.
No examples provided.
midi_to_note ~44
Returns the note and octave for a given MIDI note number - the inverse of note_to_midi.
| Name | Type | Req | Description |
|---|---|---|---|
| midi_number | integer | yes | MIDI note number (0-127) |
No output schema declared.
No examples provided.
note_to_frequency ~61
Returns the frequency in Hz for a note at a given octave, equal temperament, A4 = 440Hz.
| Name | Type | Req | Description |
|---|---|---|---|
| note | string | yes | Note |
| octave | integer | yes | Octave (scientific pitch notation, typically -1 to 9) |
No output schema declared.
No examples provided.
note_to_midi ~67
Returns the MIDI note number for a note at a given octave, using scientific pitch notation (C4 = middle C = MIDI 60).
| Name | Type | Req | Description |
|---|---|---|---|
| note | string | yes | Note |
| octave | integer | yes | Octave (scientific pitch notation, typically -1 to 9) |
No output schema declared.
No examples provided.
resolve_interval ~42
Returns the from-note and to-note for a named interval within a root context.
| Name | Type | Req | Description |
|---|---|---|---|
| interval | string | yes | Interval ID |
| root | string | yes | Root note |
No output schema declared.
No examples provided.
transpose ~66
Transposes a set of notes from one key to another by the semitone distance between the two roots.
| Name | Type | Req | Description |
|---|---|---|---|
| from_root | string | yes | Root the notes are currently in |
| notes | array | yes | Notes to transpose |
| to_root | string | yes | Root to transpose the notes into |
No output schema declared.
No examples provided.
What is the PlayByKey Music Theory MCP server?
PlayByKey Music Theory is an MCP server listed in the public MCP registry as com.playbykey/theory-mcp. Chords, scales, progressions, transposition, and MIDI tools for music theory AI agents. This page covers its npm package (@playbykey/theory-mcp).
Is the PlayByKey Music Theory MCP server safe to use?
PlayByKey Music Theory scores 84 out of 100 on VerifyMCP. We found no known CVEs affecting it as of 23 September 2026. It declares no install or post-install scripts. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.
What tools does the PlayByKey Music Theory MCP server expose?
PlayByKey Music Theory exposes 32 tools: get_mode_notes, get_parent_scale_modes, get_modal_root, get_relative_minor, get_relative_major, and 27 more. Their descriptions and schemas cost roughly 1,749 tokens of context every time the server is loaded.
Is the PlayByKey Music Theory MCP server still maintained?
PlayByKey Music Theory is still listed as active in the MCP registry. We last reached this channel on 23 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.
What licence is the PlayByKey Music Theory MCP server under?
PlayByKey Music Theory declares the MIT licence, which is OSI-approved. That covers the source only, and says nothing about the cost of any service it calls.