Web search over MCP

The configuration

Identical across clients; only the file location differs. Claude Code reads .mcp.json in the project root or ~/.claude.json globally; Claude Desktop uses claude_desktop_config.json; Cursor uses .cursor/mcp.json.

{
  "mcpServers": {
    "unlob": {
      "command": "npx",
      "args": ["-y", "@unlob/mcp"],
      "env": { "UNLOB_API_KEY": "ulb_your_key_here" }
    }
  }
}

Keeping the key out of version control

Project-scoped configs are worth committing so a team shares the same tools — which means the key must not be in the file. Reference an environment variable and export it from your shell profile or a gitignored .env.

Keys are ulb_ followed by 48 hex characters, stored as a hash on our side and shown once. If one leaks, rotate it: rotation issues a replacement and retires the old key in one transaction, so there is never a window with two live keys or none.

What the agent gets

Five retrieval tools: web_search, get_document, similar, browse and why_not. Six graph tools: related, corroborate, authorities, dossier, path and assemble_context.

Models generally reach for web_search by default. The graph tools need a nudge in the system prompt, and they are where the difference from any other search MCP server actually lies.

Prompting for the graph tools

A short instruction is enough, and it changes behaviour substantially: use corroborate before stating anything as fact; use why_not before concluding something does not exist; use authorities when entering an unfamiliar topic; use assemble_context when a question needs many sources rather than one.

Without this, an agent will search repeatedly and reconstruct in context what a single graph call would have answered.

When the tools do not appear

Almost always a JSON syntax error, or a missed restart — configs are read at startup. If you already had MCP servers configured, check that the new entry merged into the existing mcpServers object rather than replacing it.

In Claude Code, /mcp lists connected servers and their tools, which is the fastest way to confirm.