# Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory (remote · assay.agentdiet.dev)

Live behavioral security verifier, schema auditor, and trust oracle for A2A, MCP & x402 agents.

- Trust score: 89/100 (high trust)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-11-05

## Components

- remote · `assay.agentdiet.dev`: 89/100 (this document), [markdown](https://verifymcp.io/servers/dev-agentdiet-assay/assay.md), [page](https://verifymcp.io/servers/dev-agentdiet-assay/assay)

## Channel facts

- Endpoint: `https://assay.agentdiet.dev/mcp`
- Transports: `streamable-http`
- Auth: `required (not validated)`
- Version: `7.0.17`

## 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 2026-11-05.

- **Endpoint Security**: 91/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - Authorisation is enforced on tool calls, but the challenge carries no valid RFC 9728 metadata, so a client cannot discover where to get a token.
  - 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**: 95/100
  - 100% of prompts and resources have a non-trivial description (not blank, and not just the item's name).
  - AI-judged instruction clarity (excellent).
  - Tool/resource definitions use about 1454 tokens (~103/item across 14 items; 4 tools + 10 resources), lean.
  - Tools include usage examples.
- **Stability & Change Management**: 57/100
  - Stability observed for 17 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **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 4 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).
  - Supports UI / widget rendering.

## Install

### How do I install the Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory server?

Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory is a hosted endpoint at https://assay.agentdiet.dev/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 dev-agentdiet-assay 'https://assay.agentdiet.dev/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "dev-agentdiet-assay": {
      "url": "https://assay.agentdiet.dev/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "dev-agentdiet-assay": {
      "type": "http",
      "url": "https://assay.agentdiet.dev/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.dev-agentdiet-assay]
url = "https://assay.agentdiet.dev/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "dev-agentdiet-assay": {
      "type": "remote",
      "url": "https://assay.agentdiet.dev/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add dev-agentdiet-assay --url 'https://assay.agentdiet.dev/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  dev-agentdiet-assay:
    url: "https://assay.agentdiet.dev/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "dev-agentdiet-assay": {
      "Transport": "http",
      "Url": "https://assay.agentdiet.dev/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add dev-agentdiet-assay -t streamable-http -u 'https://assay.agentdiet.dev/mcp'
```

### Other

```json
{
  "mcpServers": {
    "dev-agentdiet-assay": {
      "type": "http",
      "url": "https://assay.agentdiet.dev/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.

### 2026-11-03 (score 89, +1)

No change was recorded against any check on this day. Stability & Change Management went from 47 to 50. That category is still filling its 30-day observation window: 14 days of observed history at the previous scan, 15 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-11-01 (score 88, +1)

No change was recorded against any check on this day. Stability & Change Management went from 40 to 43. That category is still filling its 30-day observation window: 12 days of observed history at the previous scan, 13 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-30 (score 87, +1)

No change was recorded against any check on this day. Stability & Change Management went from 33 to 37. That category is still filling its 30-day observation window: 10 days of observed history at the previous scan, 11 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-28 (score 86, +1)

No change was recorded against any check on this day. Stability & Change Management went from 27 to 30. That category is still filling its 30-day observation window: 8 days of observed history at the previous scan, 9 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-26 (score 85, +1)

No change was recorded against any check on this day. Stability & Change Management went from 20 to 23. That category is still filling its 30-day observation window: 6 days of observed history at the previous scan, 7 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-24 (score 84, +1)

No change was recorded against any check on this day. Stability & Change Management went from 13 to 17. That category is still filling its 30-day observation window: 4 days of observed history at the previous scan, 5 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-22 (score 83, +1)

No change was recorded against any check on this day. Stability & Change Management went from 7 to 10. That category is still filling its 30-day observation window: 2 days of observed history at the previous scan, 3 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-21 (score 82, +1)

- [security improvement] DNSSEC: fail → pass

## MCP tools (4)

### `assay_preflight` (~281 tokens)

Pre-Flight MCP & A2A Security Gate

Gate a remote MCP, A2A, or x402 endpoint before calling or paying it by probing live JSON-RPC reachability, hashing tools/list (SHA-256), and scanning for prompt-injection poisoning. When expected_tools_hash is provided, any mismatch against the live tools/list digest forces verdict='deny' to block silent schema rug-pulls; when omitted, verdict reflects liveness and injection safety alone. Read-only gate; first 5 calls/IP are free and quota-exceeded calls return a 402 top-up prompt. Use before tool execution or payment; to register or refresh public leaderboard telemetry use assay_probe; to read or pin stored policy hashes use assay_get_ledger_policy; after payment use assay_verify_delivery. Example: target='https://agentdiet-72343955726.us-central1.run.app/mcp'.

Input parameters:

- `expected_tools_hash` (string): Optional 64-char SHA-256 hex digest of the canonical MCP tools/list schema from mcp-lock.json. Omit to read or auto-pin the current live digest; pass a 64-hex digest to enforce zero-drift gating.
- `target` (string, required): Public HTTPS URL of the remote MCP server, A2A agent, or x402 endpoint to inspect (e.g. 'https://tandem.ac/mcp'). Private and loopback IPs are blocked.

Output parameters:

- `dossier` (object)
- `error` (string|null)
- `reason` (string)
- `receipt` (string)
- `status` (string)
- `verdict` (string)

### `assay_probe` (~230 tokens)

Register & Refresh Endpoint Conformance Telemetry

Register a new remote MCP, A2A, or x402 endpoint or refresh its public Assay Observatory dossier by running a live HTTP, agent-card, and JSON-RPC tools/list inspection without policy gating. Target must be a public HTTPS origin (private IPs are rejected with a 400 error); each call appends a timestamped observation and increments rug_pulls if tools_hash drifted since the prior stored observation. Writes to the public ledger; first 5 calls/IP are free and retries are idempotent on steady schemas. Use to onboard or re-index a server; for pre-call allow/deny gating use assay_preflight; for historical observations or hash pinning use assay_get_ledger_policy; for post-payment disputes use assay_verify_delivery. Example: target='https://agentdiet-72343955726.us-central1.run.app/mcp'.

Input parameters:

- `target` (string, required): Public HTTPS URL of the remote MCP server, A2A agent, or x402 endpoint to inspect (e.g. 'https://tandem.ac/mcp'). Private and loopback IPs are blocked.

Output parameters:

- `dossier` (object)
- `error` (string|null)
- `reason` (string)
- `receipt` (string)
- `status` (string)
- `verdict` (string)

### `assay_verify_delivery` (~313 tokens)

Verify Post-Payment x402 Delivery & Mint SLA Receipt

Audit a paid x402 or A2A provider after payment to confirm delivery or prove an SLA breach with an HMAC-SHA256 signed receipt. Passing status_code >= 500 forces verdict='sla_breach_confirmed' even if the live re-probe succeeds, while passing tx_hash cryptographically binds your Base or Solana payment signature into the receipt (omitting tx_hash still verifies liveness and issues a probe-bound receipt). Non-destructive; first 5 calls/IP are free and failed target connections do not throw tool errors. Use only after paying a provider; before payment use assay_preflight; for public indexing use assay_probe; for policy history use assay_get_ledger_policy. Example: target='https://agentdiet-72343955726.us-central1.run.app/mcp'.

Input parameters:

- `status_code` (string): Optional HTTP status code returned by the paid endpoint (e.g. '200', '502', '504'). Codes >= 500 force verdict='sla_breach_confirmed' even if a retry probe succeeds.
- `target` (string, required): Public HTTPS URL of the remote MCP server, A2A agent, or x402 endpoint to inspect (e.g. 'https://tandem.ac/mcp'). Private and loopback IPs are blocked.
- `tx_hash` (string): Optional on-chain payment transaction hash (0x Base USDC hash or base58 Solana signature) to bind into the signed SLA receipt. Omit to run an unsigned post-call SLA check.

Output parameters:

- `dossier` (object)
- `error` (string|null)
- `reason` (string)
- `receipt` (string)
- `status` (string)
- `verdict` (string)

### `assay_get_ledger_policy` (~271 tokens)

Query Historical Ledger & Pin Expected Schema Hashes

Retrieve historical conformance observations and manage pinned SHA-256 tools/list policy hashes in the Assay ledger for a target endpoint. When expected_tools_hash is provided, it pins that 64-hex digest as the target's baseline policy and compares it against the latest stored observation; when omitted, it returns the stored dossier and last 20 drift observations without network probing unless the target is unindexed. Idempotent; first 5 calls/IP are free. Use to audit historical drift or pin mcp-lock.json hashes; for live pre-execution gating use assay_preflight; for live re-indexing use assay_probe; for post-payment SLA receipts use assay_verify_delivery. Example: target='https://agentdiet-72343955726.us-central1.run.app/mcp'.

Input parameters:

- `expected_tools_hash` (string): Optional 64-char SHA-256 hex digest of the canonical MCP tools/list schema from mcp-lock.json. Omit to read or auto-pin the current live digest; pass a 64-hex digest to enforce zero-drift gating.
- `target` (string, required): Public HTTPS URL of the remote MCP server, A2A agent, or x402 endpoint to inspect (e.g. 'https://tandem.ac/mcp'). Private and loopback IPs are blocked.

Output parameters:

- `dossier` (object)
- `error` (string|null)
- `reason` (string)
- `receipt` (string)
- `status` (string)
- `verdict` (string)

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/dev-agentdiet-assay/assay#diagnostics

## Score history

- 2026-11-05: 89
- 2026-11-04: 89
- 2026-11-03: 89
- 2026-11-02: 88
- 2026-11-01: 88
- 2026-10-31: 87
- 2026-10-30: 87
- 2026-10-29: 86
- 2026-10-28: 86
- 2026-10-27: 85
- 2026-10-26: 85
- 2026-10-25: 84
- 2026-10-24: 84
- 2026-10-23: 83
- 2026-10-22: 83
- 2026-10-21: 82
- 2026-10-20: 81
- 2026-10-19: 76

## Common questions

### What is the Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory server?

Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory is listed in the public MCP registry as dev.agentdiet/assay. Live behavioral security verifier, schema auditor, and trust oracle for A2A, MCP & x402 agents. This page covers its hosted endpoint (https://assay.agentdiet.dev/mcp).

### Is the Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory server safe to use?

Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory scores 89 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 Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory server expose?

Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory exposes 4 tools: assay_preflight, assay_probe, assay_verify_delivery, assay_get_ledger_policy. Their descriptions and schemas cost roughly 1,095 tokens of context every time the server is loaded.

### Does the Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory server require authentication?

Yes. Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory asked us for credentials when we connected, so you will need to authorise it in your MCP client before it can do anything.

### Is the Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory server still maintained?

Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory is still listed as active in the MCP registry. We last reached this channel on 5 November 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://assay.agentdiet.dev/mcp
- Repository: https://github.com/robertoyanguas-ops/assay
- Website: https://assay.agentdiet.dev/
- Changelog RSS feed: https://verifymcp.io/servers/dev-agentdiet-assay/assay.xml
- Changelog JSON feed: https://verifymcp.io/servers/dev-agentdiet-assay/assay.json
- HTML version of this page: https://verifymcp.io/servers/dev-agentdiet-assay/assay