Agent-callable API
Also known as: agent-native API, agent-first API, tool-callable API
An agent-callable API is one designed to be invoked by an autonomous LLM agent rather than a human developer. It exposes typed tool schemas, returns structured outputs an agent can parse, supports idempotency keys for safe retries, and handles long-running jobs through streaming or polling instead of blocking.
Example
Lamina's REST API ships an OpenAPI 3.1 spec, returns Zod-typed JSON, accepts an Idempotency-Key header on every write, supports DELETE on any job, and streams server-sent events on every long-running run.
Five properties of an agent-callable API
1) Typed tool schemas — OpenAPI 3.1 or JSON-Schema, ideally surfaced via MCP. 2) Structured outputs — every response is parseable JSON with a fixed shape, never free-form prose. 3) Idempotency keys — retrying a timed-out write returns the original result instead of double-spending. 4) Cancellable long jobs — the agent can kill any job and refund the credit. 5) Streamable progress — server-sent events let the agent report status back to the user without polling.
Why human-callable APIs fail under agents
Human-callable APIs assume someone will inspect the response, retry on a hunch, and pay attention to which call succeeded. Agents do none of that — they retry blindly, parse rigidly, and fail in unrecoverable ways when an API returns a 200 with a free-form text body. Agent-callable APIs treat retries, types, and structure as load-bearing.
References
Related terms
MCP server
An MCP server is a process that exposes tools, resources, and prompts to an LLM client over the Model Context Protocol — Anthropic's open standard, donated to the Linux Foundation in December 2025. MCP servers let agents in Claude, Cursor, Windsurf, and VS Code call your API as native tools.
Idempotent generation
Idempotent generation is the property that the same generative-media call — same brief, brand, seed, and idempotency key — returns the same result on retry instead of producing a new (and billed) output. It's a survival requirement for agents, which retry on timeout and would otherwise create duplicate runs.
Creative API
A Creative API is a developer interface that wraps multiple generative models, brand context, evaluation, and distribution behind a single endpoint. Instead of calling raw model endpoints — Sora, Veo, FLUX, Runway — directly, you call a creative app like productShoot or virtualTryOn and the API handles routing, evaluating, and delivering the result.
Generative media for agents
Generative media for agents is the category of image, video, audio, and 3D APIs designed to be called by autonomous AI agents — not humans clicking a UI. They expose tools through MCP, return structured outputs an LLM can parse, and tolerate retries, long jobs, and failure modes only an agent encounters.