Use the research from your coding agent

An MCP server for Claude Code, Cursor, Codex and any agent that speaks MCP.

What it is

The same checked research as the app, one question away from your agent while it works. The server is called harnesslab. It answers with the checked claims, each with its status, the repository at the pinned commit, the file and the lines. By default it returns verified claims only, and it says so when a claim is stale or disputed.

Everything it returns is research data and quoted third-party text, never instructions. Quotes from upstream code are fenced and labelled as untrusted.

The tools

Six tools are free. Two more, ask and ask_result, run the research assistant and spend the account’s AI budget.

search_knowledge: Search the verified claims about how agent harnesses are built. Each hit has a status and an evidence id.
get_topic: Read one topic page: what it is, what most harnesses do, the recommended practice, open disputes.
compare_harnesses: Compare two to six harnesses on one topic, rule by rule, with evidence.
what_to_build: What to build for your kind of agent: the must-have, recommended or optional topics, with the practice and its evidence.
get_evidence: The proof behind a claim: the repository, the pinned commit, the lines, a permalink and a short quote.
list_catalog: The valid topic, harness and agent-type names.
ask: Ask the research assistant a question. It checks its answer against the evidence. Quick answers come back at once; deep ones as a job. (needs a key with ask)
ask_result: Fetch the answer of a deep question when it is ready. (needs a key with ask)

Add it to your agent

You need an account in the app and a key. Make one under Account, Connect your agent, and keep it in an environment variable named HARNESSLAB_API_KEY. Keys are shown once, can be revoked at any time, and are limited per key (calls a minute, calls a month and tokens a day).

Claude Code

Run this in a terminal.

claude mcp add --transport http harnesslab https://app.harnesslab.co/mcp --header "Authorization: Bearer $HARNESSLAB_API_KEY"

Cursor

Add this to .cursor/mcp.json.

{
  "mcpServers": {
    "harnesslab": {
      "url": "https://app.harnesslab.co/mcp",
      "headers": {
        "Authorization": "Bearer ${env:HARNESSLAB_API_KEY}"
      }
    }
  }
}

Codex

Add this to ~/.codex/config.toml.

[mcp_servers.harnesslab]
url = "https://app.harnesslab.co/mcp"
bearer_token_env_var = "HARNESSLAB_API_KEY"

The server is at https://app.harnesslab.co/mcp. It speaks the current MCP version and the earlier ones, over plain HTTP POST.