brydge-mcp

Check whether your agent's work actually happened.

This is BRYDGE as an MCP server. Before an agent acts, BRYDGE decides whether it may. Afterwards, BRYDGE reads the destination system's own records, such as your payment processor or ticket system, using its own credential. It then reports whether the work happened as permitted. What the agent says happened is kept beside that finding and never decides it.

Tools

Tool	What it does
brydge_supervise	Asks before acting. ALLOWED returns an authorization id for the agent to write into the record the action creates. ESCALATED means a person decides, and the agent must not act.
brydge_report_outcome	Reports what the agent believes happened.
brydge_verify	Reads the destination's records now and says whether the work happened.
brydge_get_finding	Returns what BRYDGE has found so far, without reading the records again. Free.
brydge_get_headroom	Says how many actions the agent may take in any 24 hours before a person is asked.

The server also gives the model its instructions: ask first, cite the authorization, report, then verify before saying the work is done.

Set up BRYDGE first

Do these once, in BRYDGE:

1. Issue an API key on the Connect page.
2. Declare what the action is worth. BRYDGE charges a share of that value, and it will not check an action nobody has priced.
3. Register a destination for the action: where BRYDGE reads the records, and the read-only credential it uses. BRYDGE has a preset for Stripe refunds.
4. Issue a mandate to the agent for the action. Without one, every call goes to a person.

A mandate says what the agent may do; headroom says how much of it, in any 24 hours. A new agent starts with room for one action a day, and every report BRYDGE checks and finds true raises that.

Add it to your MCP client

Most clients take this configuration (Claude Desktop, Cursor, Windsurf and others):

{
  "mcpServers": {
    "brydge": {
      "command": "npx",
      "args": ["-y", "brydge-mcp"],
      "env": {
        "BRYDGE_API_KEY": "brydge_sk_...",
        "BRYDGE_ACTOR": "agent:refund-ops"
      }
    }
  }
}

On Windows, npx is a .cmd file, and only clients that start commands through a shell or through the MCP SDK can launch it by name. If your client reports spawn npx ENOENT, start it through the command shell instead:

{
  "mcpServers": {
    "brydge": {
      "command": "cmd",
      "args": ["/c", "npx", "-y", "brydge-mcp"],
      "env": {
        "BRYDGE_API_KEY": "brydge_sk_...",
        "BRYDGE_ACTOR": "agent:refund-ops"
      }
    }
  }
}

In Claude Code:

claude mcp add brydge -e BRYDGE_API_KEY=brydge_sk_... -e BRYDGE_ACTOR=agent:refund-ops -- npx -y brydge-mcp

Setting
BRYDGE_API_KEY	Your BRYDGE API key. Required.
BRYDGE_ACTOR	The name BRYDGE knows this agent by, such as agent:refund-ops. Mandates are issued to this name. Required.
BRYDGE_URL	Where BRYDGE runs. Leave it unset for BRYDGE's hosted service.

The agent's name comes from this configuration, never from the model, so an agent cannot borrow another agent's permissions. Run one server per agent.

How an agent uses it

1. Ask first. Before a refund, payment or other change, the agent calls brydge_supervise with the action, the target and the facts, such as {"amount": 4200}.
2. Cite the authorization. If the answer is ALLOWED, the agent carries the action out and writes the authorization id where the destination keeps it. For a Stripe refund, that is metadata.brydge_authorization. BRYDGE finds the work by this id, and by nothing else.
3. Report. The agent calls brydge_report_outcome with what it believes happened.
4. Verify. Before saying the work is done, the agent calls brydge_verify.

brydge_supervise takes an idempotency_key, a name for one intended action such as refund:ch_123. Retrying with the same key gets the same answer. A key reused for a different action never gets another action's answer, because the server also hashes in what is being asked.

What a check can find

state	Meaning
VERIFIED	The records show the work, as it was permitted.
FAILED	The records show it was attempted and did not succeed.
MISMATCH	The records show something other than what was permitted. reason says what: AMOUNT, TARGET, ACTOR, ACTION, DUPLICATE_EXECUTION, UNAUTHORISED_EXECUTION or CORRELATION.
UNKNOWN	BRYDGE could not tell. NO_MATCH means the records hold nothing for this authorization; the other reasons mean BRYDGE could not read the records. Unknown is not the same as failed.
PENDING	The destination says the work is still in progress.

brydge_verify reads the records when it is called. A check that finds something new is billed; asking again when nothing has changed is free. BRYDGE also checks every action by itself once the destination's reporting window has passed (60 minutes unless you set another), and brydge_get_finding reads that for free.

Protocol

The server speaks MCP over stdio. It serves clients on the 2026-07-28 revision and on the 2025 revisions from the same process, built on the official TypeScript SDK. When BRYDGE cannot be asked (a bad key, an action with no declared value, a rate limit, or BRYDGE being unreachable), the tool returns an error the model can read, and nothing is carried out.

Limits

• BRYDGE treats a target as one piece of work. A second record for the same target that carries a different authorization, such as a second partial refund of one charge, is reported as a MISMATCH.
• The server does not wait for a person. An escalated action ends with the model being told a person decides, and a later request is decided afresh.

Development

npm install
npm test          # a real MCP client against the server in both protocol eras, and the built command over stdio
npm run test:int  # against a running BRYDGE; see tests/integration
npm run build

License

MIT