# io.github.cyanheads/browser-compat-mcp-server (remote · browser-compat.caseyjhand.com)

Browser compatibility and Baseline status for any web feature — offline, from bundled MDN data.

- Trust score: 67/100 (medium)
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-09-20

## Components

- remote · `browser-compat.caseyjhand.com`: 67/100 (this document), [markdown](https://verifymcp.io/servers/cyanheads-browser-compat-mcp-server/browser-compat.md), [page](https://verifymcp.io/servers/cyanheads-browser-compat-mcp-server/browser-compat)
- npm · `@cyanheads/browser-compat-mcp-server`: 38/100, [markdown](https://verifymcp.io/servers/cyanheads-browser-compat-mcp-server/cyanheads-browser-compat-mcp-server.md), [page](https://verifymcp.io/servers/cyanheads-browser-compat-mcp-server/cyanheads-browser-compat-mcp-server)

## Channel facts

- Endpoint: `https://browser-compat.caseyjhand.com/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `0.1.3`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-09-20.

- **Endpoint Security**: 66/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - Authorisation not fully verified: no authorisation is required to call this server, and 5 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe.
  - HTTPS is enforced; there's no plaintext access path.
  - The HSTS (Strict-Transport-Security) header is present.
  - DNSSEC is configured correctly; the domain's records validate against the full chain to the root.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 68/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 1269 tokens (~253/item across 5 items; 5 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 0/100
  - Stability not yet verified: not enough scan history yet (needs a 30-day window).
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
  - Structured output schemas are declared (100% of tools); any adoption earns full credit.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 5 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 6 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a current MCP spec version (2026-07-28).

**Unverified: 1 category.** A category scored 0 because we could not verify it: authentication we do not have, an unreachable endpoint, or not enough scan history. We only credit what we can confirm.

## Install

### How do I install the io.github.cyanheads/browser-compat-mcp-server server?

io.github.cyanheads/browser-compat-mcp-server is a hosted endpoint at https://browser-compat.caseyjhand.com/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add --transport http cyanheads-browser-compat-mcp-server 'https://browser-compat.caseyjhand.com/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "cyanheads-browser-compat-mcp-server": {
      "url": "https://browser-compat.caseyjhand.com/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "cyanheads-browser-compat-mcp-server": {
      "type": "http",
      "url": "https://browser-compat.caseyjhand.com/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.cyanheads-browser-compat-mcp-server]
url = "https://browser-compat.caseyjhand.com/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "cyanheads-browser-compat-mcp-server": {
      "type": "remote",
      "url": "https://browser-compat.caseyjhand.com/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add cyanheads-browser-compat-mcp-server --url 'https://browser-compat.caseyjhand.com/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  cyanheads-browser-compat-mcp-server:
    url: "https://browser-compat.caseyjhand.com/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "cyanheads-browser-compat-mcp-server": {
      "Transport": "http",
      "Url": "https://browser-compat.caseyjhand.com/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add cyanheads-browser-compat-mcp-server -t streamable-http -u 'https://browser-compat.caseyjhand.com/mcp'
```

### Other

```json
{
  "mcpServers": {
    "cyanheads-browser-compat-mcp-server": {
      "type": "http",
      "url": "https://browser-compat.caseyjhand.com/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-09-20 (score 67)

First indexed and scored.

## MCP tools (5)

### `browsercompat_list_reference` (~161 tokens)

Browsercompat List Reference

Enumerate the reference vocabulary this server uses: BCD namespaces, BCD browser ids, browserslist agent ids and their BCD counterparts, Baseline states, web-features groups, and ECMAScript snapshots. Use it to build valid inputs for the other tools and to see which target browsers can be evaluated.

Input parameters:

- `topic` (string, required): Which vocabulary to list: bcd_namespaces for the 12 top-level browser-compat-data namespaces, bcd_browsers for the 17 tracked browsers, browserslist_agents for the 19 browserslist ids mapped to brows…

Output parameters:

- `attribution` (string): Required attribution for the caniuse-derived usage figures in this response.
- `data_version` (object): Vintage of each bundled dataset behind this answer.
- `entries` (array): Every entry in the requested vocabulary.
- `error` (object): Present when the call failed. Absent on success.
- `topic` (string): The topic that was listed.

### `browsercompat_get_feature` (~254 tokens)

Browsercompat Get Feature

Get the compatibility record for one web feature: Baseline state and the date it crossed, deprecation and standards status, per-browser version added and removed with flags, vendor prefixes and partial-implementation notes, and the MDN and specification links. Accepts a BCD key such as css.selectors.has or a web-features id such as has; the response echoes which one it matched. An unresolved feature returns found: false with guidance rather than an error.

Input parameters:

- `feature` (string, required): A browser-compat-data key such as css.selectors.has, or a web-features id such as has, 1 to 200 characters. An empty or longer string is rejected against this schema; a whitespace-only string returns…
- `include_runtimes` (boolean): Add the bun, deno, nodejs, and oculus rows to support. Leave off for browser ship decisions.
- `resolve` (boolean): When true, fall back to the search index and accept its single unambiguous top hit. Off by default so a typo returns a miss you can correct rather than a confident answer about the wrong feature.

Output parameters:

- `baseline` (object): Baseline state for the resolved key, or the feature rollup when a web-features id resolved to more than one key.
- `baselineNotMapped` (string): Explains why a resolved key carries no Baseline state.
- `compat_keys` (array): Present when the web-features id spans more than one browser-compat-data key. Call this tool again with one of them for the per-browser fields.
- `data_version` (object): Vintage of each bundled dataset behind this answer.
- `description` (string): web-features description, or the browser-compat-data description with tags stripped.
- `error` (object): Present when the call failed. Absent on success.
- `found` (boolean): True when the feature string resolved to a tracked entry.
- `guidance` (string): What to do next on a miss or with no compat data.
- `limiting_browser` (object): Among the Baseline core browsers, the one requiring the newest release. Absent until every core browser has shipped a resolvable version.
- `mdn_url` (string): MDN reference page for the resolved key.
- `name` (string): web-features display name for the feature.
- `outcome` (string): found when per-feature data was returned, no_compat_data when the entry is tracked but owns no browser-compat-data keys, miss when nothing matched.
- `resolved_as`: How the feature string was matched, or null on a miss.
- `runtimesExcluded` (string): Notes that the feature carries server-runtime or XR data that was left out.
- `spec_urls` (array): Specification URLs for the resolved key, always an array.
- `status` (object): Standards status for the resolved key. Absent for webextensions keys, which record none, and when the id spans more than one key.
- `support` (array): One row per reported browser. Absent when the id spans more than one browser-compat-data key.

### `browsercompat_check_baseline` (~196 tokens)

Browsercompat Check Baseline

Check whether web features are safe to ship: Baseline state and the date it crossed, the browser and version that limits support, whether the feature is deprecated or discouraged, and the share of tracked global traffic that requiring it would exclude. Accepts up to 20 BCD keys or web-features ids in one call.

Input parameters:

- `features` (array, required): Up to 20 entries, each a browser-compat-data key such as css.selectors.has or a web-features id such as has, 1 to 200 characters. An empty or longer entry is rejected against this schema; a whitespac…
- `resolve` (boolean): When true, fall back to the search index and accept its single unambiguous top hit for each entry. Off by default so a typo returns a miss you can correct.

Output parameters:

- `all_widely_available` (boolean): True only when every entry resolved and reports Baseline widely. A single miss forces false. Deprecation and discouragement do not enter this answer.
- `attribution` (string): Required attribution for the caniuse-derived usage figures in this response.
- `data_version` (object): Vintage of each bundled dataset behind this answer.
- `error` (object): Present when the call failed. Absent on success.
- `results` (array): One result per requested feature. A miss is a result, not a failure.
- `totalCount` (number): Number of results returned.
- `unresolvedNotice` (string): Names the entries that did not resolve and how to find the right key.

### `browsercompat_search_features` (~168 tokens)

Browsercompat Search Features

Find web features by plain name or keyword when the canonical key is unknown, across CSS, JavaScript, HTML, Web APIs, SVG, MathML, WebAssembly, and HTTP headers. Returns ranked matches with the BCD key, the web-features id, the Baseline state, a one-line support summary, and which field matched. Feed a result key into browsercompat_get_feature for the full record.

Input parameters:

- `baseline` (string): Restrict results to one Baseline state.
- `limit` (integer): Maximum results to return, from 1 to 50.
- `namespace` (string): Restrict results to one top-level browser-compat-data namespace.
- `query` (string, required): Plain-language name or keyword, for example "container query" or "fromAsync".

Output parameters:

- `appliedFilters` (object): Filters the server applied to this search.
- `cap` (number): The limit that was applied.
- `data_version` (object): Vintage of each bundled dataset behind this answer.
- `error` (object): Present when the call failed. Absent on success.
- `noMatchNotice` (string): How to broaden a search that matched nothing.
- `results` (array): Ranked matches, best first. An empty array is a successful search with no hits.
- `shown` (number): Number of results returned.
- `totalCount` (number): Matches before the display cap was applied.
- `truncated` (boolean): True when matches exceeded limit.

### `browsercompat_compare_support` (~261 tokens)

Browsercompat Compare Support

Compute whether a set of web features clears an explicit browserslist target query. Returns a per-feature verdict, the target browser and version that fails, the share of tracked traffic the targets cover, and unchecked_targets for every resolved target browser with no compatibility data. A feature is never reported as clearing a target the server could not evaluate.

Input parameters:

- `features` (array, required): Up to 20 entries, each a browser-compat-data key such as css.selectors.has or a web-features id such as has, 1 to 200 characters. An empty or longer entry is rejected against this schema; a whitespac…
- `resolve` (boolean): When true, fall back to the search index and accept its single unambiguous top hit for each entry. Off by default so a typo returns a miss you can correct rather than a confident answer about the wro…
- `targets` (string, required): A browserslist query, for example "defaults" or "> 0.5%, last 2 versions", 1 to 500 characters. Required: with no query browserslist would read config from the process working directory rather than f…

Output parameters:

- `all_clear` (boolean): True only when every feature clears and unchecked_targets is empty.
- `attribution` (string): Required attribution for the caniuse-derived coverage figures in this response.
- `data_version` (object): Vintage of each bundled dataset behind this answer.
- `error` (object): Present when the call failed. Absent on success.
- `query_echo` (string): The targets query as the server parsed it.
- `results` (array): Per-feature verdicts against the resolved targets.
- `target_coverage_percent` (number): Share of tracked global traffic the evaluated targets cover.
- `targets_resolved` (array): Every browserslist token that was evaluated.
- `totalCount` (number): Number of feature results returned.
- `uncheckedNotice` (string): Names the target agents that were not evaluated and their combined usage share.
- `unchecked_coverage_percent` (number): Share of tracked global traffic the unevaluated targets cover.
- `unchecked_targets` (array): Every target the server declined to claim a verdict for, with the reason.

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/cyanheads-browser-compat-mcp-server/browser-compat#diagnostics

## Score history

- 2026-09-20: 67

## Common questions

### What is the io.github.cyanheads/browser-compat-mcp-server server?

io.github.cyanheads/browser-compat-mcp-server is listed in the public MCP registry as io.github.cyanheads/browser-compat-mcp-server. Browser compatibility and Baseline status for any web feature, offline, from bundled MDN data. This page covers its hosted endpoint (https://browser-compat.caseyjhand.com/mcp).

### Is the io.github.cyanheads/browser-compat-mcp-server server safe to use?

io.github.cyanheads/browser-compat-mcp-server scores 67 out of 100 on VerifyMCP. 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 io.github.cyanheads/browser-compat-mcp-server server expose?

io.github.cyanheads/browser-compat-mcp-server exposes 5 tools: browsercompat_list_reference, browsercompat_get_feature, browsercompat_check_baseline, browsercompat_search_features, browsercompat_compare_support. Their descriptions and schemas cost roughly 1,040 tokens of context every time the server is loaded.

### Does the io.github.cyanheads/browser-compat-mcp-server server require authentication?

No. We connected to io.github.cyanheads/browser-compat-mcp-server without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the io.github.cyanheads/browser-compat-mcp-server server still maintained?

io.github.cyanheads/browser-compat-mcp-server is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

## Links

- Remote endpoint: https://browser-compat.caseyjhand.com/mcp
- Changelog RSS feed: https://verifymcp.io/servers/cyanheads-browser-compat-mcp-server/browser-compat.xml
- Changelog JSON feed: https://verifymcp.io/servers/cyanheads-browser-compat-mcp-server/browser-compat.json
- HTML version of this page: https://verifymcp.io/servers/cyanheads-browser-compat-mcp-server/browser-compat