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Custom functions are Clay functions your team builds in the Clay UI, then runs from agents, the CLI, MCP, or the API.

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What custom functions are good for

  • Team-specific enrichment waterfalls.
  • Account scoring and qualification.
  • Inbound routing and territory logic.
  • CRM hygiene and validation.
  • Repeatable research workflows.
  • Internal tools that need the same Clay logic your GTM team already trusts.

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Runs and batch runs

The key distinction is where the function is built:
  • Build and manage the function in the Clay UI.
  • Run and batch-run it programmatically from agents, the CLI, MCP, or API.

Encode Clay functions into business systems

Call custom functions from backend services, queues, and internal tools.

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Expose a function

To call a custom function:
  1. Open Functions.
  2. Create or select a function.
  3. Open Details.
  4. Enable the integrations you need, such as API or MCP.
  5. Copy the t_... function id.
  6. Prefix it with function: when you call it from the plugin, CLI, MCP, or API.
Custom function routine ids use the format function:t_....