mcp-evidence-api

An MCP server that makes backend/API requests and packages request+response pairs as evidence — proving an endpoint works. Sibling project to mcp-evidence, which does the same thing for browser/UI flows; this one is for testing backend behavior with no browser involved (video/trace don't mean anything without a page, so this is a separate, much simpler tool rather than an extension of that one).

Generic and reusable: no assumptions about any particular API. You pass a baseUrl per session, and evidence is written into the consuming project's working directory at .evidence/<featureName>/<timestamp>/.

Install

Register with Claude Code

Per-user (available in every project):

claude mcp add --scope user evidence-api -- npx -y github:meovan07/mcp-evidence-api

Or per-project, add to .mcp.json:

{
  "mcpServers": {
    "evidence-api": {
      "command": "npx",
      "args": ["-y", "github:meovan07/mcp-evidence-api"]
    }
  }
}

This repo is public, so no GitHub credentials are needed on the machine running npx.

Consuming projects should add .evidence/ to their own .gitignore.

Related MCP server: mcp-server-apidebug

Tools

A session left open for 10 minutes with no tool calls is auto-finished. The server also flushes any open sessions on SIGINT/SIGTERM so evidence isn't lost if the process is killed mid-run.

Sensitive request/response headers (authorization, cookie, set-cookie, x-api-key, api-key, x-auth-token, proxy-authorization) are redacted before being written to disk. This only covers header names — if an endpoint echoes a secret back inside a JSON response body, that isn't redacted, since there's no reliable way to tell a secret-looking field from a normal one. Don't point this at endpoints that echo credentials in response bodies without being aware evidence files will contain them in plaintext.

Example

start_evidence_session({ featureName: "users api", baseUrl: "http://localhost:4000" })
  -> sessionId, evidenceDir

request({ sessionId, name: "create user", method: "POST", url: "/users", body: { name: "Ada" } })
request({ sessionId, name: "get user", method: "GET", url: "/users/1" })
finish_evidence_session({ sessionId, summary: "Users API create+fetch works" })

Resulting evidence directory:

.evidence/users-api/2026-07-08T08-41-21-754Z/
  requests.json
  manifest.json

requests.json is an array of full request/response records (method, url, headers, body, status, timing). manifest.json is a summary: request count and how many came back non-2xx.

query (database verification)

An API response can claim an action succeeded without the database actually reflecting it correctly (soft-deletes, audit fields, related-table writes). query lets you check the real state directly — currently Postgres only.

Setup: set DATABASE_URL as an environment variable on the MCP server registration, same pattern as the IMAP credentials — run this yourself, don't have an agent run it or inspect it afterward:

claude mcp add --scope user evidence-api \
  -e DATABASE_URL=postgres://user:password@host:5432/dbname \
  -- npx -y github:meovan07/mcp-evidence-api

Read-only, enforced twice: input is rejected unless it's a single SELECT/WITH ... SELECT statement (no semicolon-separated multi-statement tricks), and every query runs inside a database-level read-only transaction (SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY), so a write hidden inside something like a CTE — which could slip past the input check — still gets rejected by Postgres itself. Validated directly: a WITH deleted AS (DELETE ... RETURNING *) SELECT * FROM deleted attempt was rejected with cannot execute SELECT in a read-only transaction, and the row was confirmed still present afterward.

query({ sessionId, name: "confirm signup row", sql: "SELECT * FROM users WHERE email = $1", params: ["ada@example.com"] })
  -> "1 row(s) (2ms)\n[{\"id\":1,\"email\":\"ada@example.com\",...}]"

Results over 50 rows are truncated in the evidence file (the tool's response still reports the true rowCount); string cell values over 2000 characters are truncated too.

wait_for_email (OTP / verification-code retrieval)

For test flows that require an email OTP (signup, login, password reset). Reads over IMAP — no browser, no Gmail login automation, nothing that breaks when a mail provider's web UI changes.

Setup: requires an IMAP-accessible mailbox and an app password (Gmail: enable 2-Step Verification, then generate one at myaccount.google.com/apppasswords). Set these as environment variables on the MCP server registration — never commit them, never put them in a tracked file:

claude mcp add --scope user evidence-api \
  -e IMAP_USER=you@gmail.com \
  -e IMAP_APP_PASSWORD=xxxxxxxxxxxxxxxx \
  -- npx -y github:meovan07/mcp-evidence-api

Run this yourself in your own terminal rather than having an agent run it — claude mcp get <name> echoes registered env vars back in plaintext, so credentials shouldn't pass through a session that might inspect it later.

(IMAP_HOST is optional, defaults to imap.gmail.com.)

Behavior: only matches emails that arrive after the tool call starts (with a small clock-skew buffer), so it never accidentally picks up a stale OTP from an earlier run. Polls until a match or timeoutMs (default 30s) elapses, then throws a clear timeout error.

wait_for_email({ subjectContains: "verification code", pattern: "\\d{6}" })
  -> "Matched: 482913 (from email \"Your verification code\" sent by noreply@yourapp.com)"

If you don't pass pattern, it returns the full email (from/subject/date/body text) instead of trying to extract a code — useful for reading a magic link URL, for example.

Security notes: the app password should be scoped to nothing but this — generate one just for this purpose, and revoke it if you ever suspect it leaked. This tool only reads mail; it can't send, delete, or modify anything. The extracted code is returned as plain text in the tool result (by design — that's how you use it), so don't point this at a mailbox that receives anything more sensitive than test/verification emails.

Development

npm install
npm run build   # tsc -> dist/
npm run dev     # tsc --watch
npm start        # node dist/index.js