API and protocol reference

Look up frame fields, callback signatures, error codes, catalog values and MCP tools here. For task-oriented guidance, start with Build an agent or Improve the agent.

• The Brain API — every callback, its signature, and what it is handed.
• The wire — every frame each end sends, and what it obliges.
• The RTVI plane — the message whitelist, both directions.
• Voice and language — the voices, the languages, and the pairing rule.
• Error codes — every code, what raised it, and whether it ends the call.
• The HTTP API — sessions.connect, and why management is MCP instead.
• The MCP server — the tools an agent gets, and what each one reads or writes.

What is checked

Contract lists and stable product claims are checked against their sources.

• The Voice and Language enums are read out of the proto descriptor by the SDK rather than written down twice, and a test fails if they drift.
• Every number, version and date on this site lives once in a facts file next to the source it was read out of, and a checker re-reads each one from that source on every run. A page may also declare the sentences that are wrong because of it, and those are searched for in the prose.
• The technical nouns come from a closed lexicon, checked the same way, so one concept keeps one word across the proto, the SDK and these pages.

Machine-readable lists are derived where a source exists; explanatory guidance remains in the task pages.