Verify Ps MCP

Verify the PlanetScale MCP server

The user-facing surface of this repo is an MCP server spoken over stdio: a client (Cursor, MCP Inspector, the hosted Gram deployment) starts src/server.ts, lists tools, and calls them. Verification means being that client — start the real server, call a real tool the way a real client would, and keep the response.

npm run lint only proves the code typechecks. It does not prove a tool returns the right fields, so it is never sufficient as a proof on its own.

Launch

There is no long-lived server to babysit. Each drive spawns its own node_modules/.bin/tsx src/server.ts child over stdio and kills it when the run ends, so runs are isolated from each other and can overlap safely.

One-time setup in a fresh checkout:

npm install
cp .env.example .env   # then fill in PLANETSCALE_API_TOKEN

The server loads .env itself through dotenv/config. Auth resolves in src/lib/auth.ts: PLANETSCALE_OAUTH2_ACCESS_TOKEN wins if set, otherwise PLANETSCALE_API_TOKEN (a <token-id>:pscale_tkn_... service token) is sent as-is. Never echo either value into a terminal, a log, or an evidence file.

Doctor

Run this first whenever anything looks wrong. It is read-only: it starts a server, initializes the MCP session, lists tools, and checks the thirteen expected tools are registered.

node .cursor/skills/verify-ps-mcp/drive.mjs doctor

Healthy output names all thirteen tools and exits 0:

OK 13 tools registered: execute_read_query, execute_write_query, get_insights, get_payment_method_setup, get_postgres_logs, get_query_tag, list_cluster_sizes, list_query_error_executions, list_query_error_patterns, list_query_tag_summaries, list_query_tags, search_documentation, update_payment_method

A crash here means the server itself is broken (a bad import, a Zod schema that throws at construction), not the tool you were investigating. Fix that before driving a feature.

Drive

node .cursor/skills/verify-ps-mcp/drive.mjs call <tool> '<json args>' \
  [--expect <substring>] [--label <name>]

--expect is what turns a drive into a check: the run exits 1 when the substring is absent from the tool's text response, so a regression fails loudly instead of printing a wrong answer that looks fine. Choose a substring that only appears when the behavior actually works — a field name the feature added, or the exact guard message a rejection should produce.

Example, sorting Insights by the Vitess bytes-received metric. Ask the user which org and database to use before filling these in:

node .cursor/skills/verify-ps-mcp/drive.mjs call get_insights \
  '{"organization":"YOUR_ORG","database":"VITESS_DATABASE","branch":"main","sort_by":"ingressBytes","limit":3,"period":"1d"}' \
  --expect '"ingress_bytes"' --label insights-ingress-vitess

Pick the command shape from features/ rather than inventing it. Those files do not name a real org or database; ask the user which ones their token can read.

Safety while driving

These tools talk to the real PlanetScale API with real credentials. Reads (get_insights, get_postgres_logs, list_query_error_patterns, list_query_error_executions, list_query_tags, get_query_tag, list_query_tag_summaries, list_cluster_sizes, search_documentation, execute_read_query) are safe against any database you own.

execute_write_query mutates real data and is not a normal verification target. Its guard rules in src/lib/query-validator.ts run before any credential is created or any connection is opened, so the rejection paths are the part you can prove for free — driving a blocked TRUNCATE touches nothing. If a change genuinely requires proving a successful write, ask the user which throwaway database to use and say so in the proof.

Evidence

Every run writes a timestamped directory under .verify/ at the repo root (gitignored) containing:

• meta.json — tool, arguments, server pid, duration, whether --expect matched
• result.json — the full MCP tool result
• result.txt — just the text content, which is what a client shows the model
• tools.json — the tool manifest (doctor runs only)
• server.stderr.log — the server's stderr for the run

A call the server rejects outright — schema validation, a transport failure, a timeout — produces no tool result, so result.json and result.txt are absent and meta.json carries an error object instead. The run still exits 1, so a rejection is a loud failure rather than a crash with no record.

A proof cites the evidence directory and quotes the fields that matter. Standards for what counts:

• Drive the tool through the MCP session, the way a client does. Importing the Gram instance and calling handleToolCall in a scratch script skips registration, schema validation, and serialization, so it proves less.
• Show the state that resulted, not only that a call returned 200. For a new response field, quote the field and its value from result.txt.
• Verify a claim on the branch it applies to. A capability that is MySQL-only needs both halves: the Vitess branch returning data, and the Postgres branch returning the refusal.
• Don't mock the PlanetScale API. It is the thing under test here.

Cleanup

Each run kills the child it spawned, so normally there is nothing to clean. Confirm and, if something was interrupted, kill the pid recorded in meta.json rather than matching on a process name (a name match would also kill the user's own npm run dev inspector session):

pgrep -fl 'src/server.ts' || echo 'no server processes left'

Evidence outlives cleanup. Prune .verify/ only when you deliberately want the old runs gone, never as part of finishing a verification.

Helpers

drive.mjs is executable and is the only helper this skill ships. It resolves the repo root from its own path, so it works from any working directory.