The agentic web

Monitoring forthe agentic web.

Your MCP server has users that never open a browser. They initialize a session, read your tool catalog, and call your tools. Yorker monitors that the same way it monitors your site: on a schedule, from real locations, speaking the real protocol.

Start Free Read Docs

mcp session · every run

# 1. initialize → protocolVersion + capabilities
→ initialize        { protocolVersion, clientInfo }
← result            { protocolVersion, capabilities }

# 2. notifications/initialized
→ notifications/initialized

# 3. tools/list → assert expected tools
→ tools/list
← result.tools       [search_docs, get_page]  ✓

# 4. tools/call → assert output
→ tools/call         search_docs { query }
← result             contains "pricing"  ✓

The failures a ping never sees

MCP servers fail in their own ways, and the failures do not move the HTTP status code. The process stays up and keeps answering 200 while everything an agent needs is broken behind it.

Broken handshake

Every MCP session starts with an initialize exchange that has to return a protocol version and the server's capabilities. If a deploy breaks it, no client gets past the first request, but the server still answers HTTP and looks healthy from the outside. Yorker sends a real initialize on every run and fails the check at that phase when the response is wrong.

Missing tool

Clients plan against the catalog your server advertises in tools/list. When a tool your integrations use drops out, nothing errors on your side; requests for it just stop working somewhere downstream. List the tools you expect in the check config and the check fails the moment one goes missing.

Changed schema

The tool exists and the server is up, but the input schema changed and callers built against the old shape now send arguments the server rejects. Yorker hashes each tool's input schema on every run and diffs it against the previous run, so a schema change becomes a reported diff instead of a slow trickle of client errors.

Wrong output

A tool can answer quickly and still be wrong. Test calls invoke a tool with arguments you choose and assert the output contains what you expect: a contract test that runs on a schedule.

Schema drift, caught on schedule

Every run hashes each tool's input schema and diffs it against the previous run. A tool that was added, removed, or changed shape shows up as a diff you can alert on, with a structured event forwarded to your OTLP backend naming the affected tools.

Failures name the phase that broke. Results carry per-phase timing for the handshake, the catalog read, and each tool call, as standard OTLP into the backend you already run.

How MCP monitoring works →

schema drift → your backend

# tools/list, hashed and diffed vs previous run
→ tools/list        [search_docs, get_page]
  missing: summarize  (present yesterday)

# forwarded to your OTLP endpoint on drift
event.name
  synthetics.mcp.schema_drift
synthetics.mcp.drift.removed_count  1
synthetics.mcp.drift.removed_tools  [summarize]

yorker.config.yaml

monitors:
  - name: Docs MCP Server
    type: mcp
    endpoint: https://mcp.example.com/mcp
    frequency: 5m
    expectedTools:
      - search_docs
      - get_page
    testCalls:
      - toolName: search_docs
        arguments: { query: pricing }
        expectedOutputContains: "Plans"
    detectSchemaDrift: true

A monitor, not a new tool

MCP checks are ordinary monitors in Yorker: same alert rules, same locations, same YAML config, same OTLP export as your HTTP and browser checks. If you already monitor your site with Yorker, adding your MCP server is a few lines of config.

An MCP session bills as one run at the HTTP rate: 10,000 HTTP + MCP runs a month free, unlimited on the paid plan.

Setup guide →

Coming soon

See your site the way an agent sees it

Browser checks that run from an AI agent's perspective: the user agent of the crawlers and agents you want to let through, on a schedule, from multiple regions, with the filmstrip showing exactly where a bot wall got in the way.

agent perspective · preview

user_agent ClaudeBot/1.0

flow homepage → product → checkout

frame 3 challenge interstitial detected

alert agents blocked at /checkout