A shortlist of APIs for tool-calling agents: search, browser control, speech, translation, messaging, and state storage.
Predictable tool use starts with the API. Stable request shapes, clean JSON, clear docs, and enough capability coverage that an agent can plan, retrieve, act, and follow up without switching providers mid-chain.
Relevant for research assistants, workflow automations, support copilots, trading tools, and multi-step developer agents. Each API listed here is realistic to call from prompts, chains, and tool routers.
Narrower landing pages cover specific subproblems: OCR, browser automation, translation, search for RAG, speech. Start here for the broadest view of reusable APIs in the directory.
