Both surfaces accept the same tengu_ key three ways, in this precedence (first present wins):
Authorization: Bearer tengu_... — recommended (works with the OpenAI/Anthropic SDKs and most HTTP clients).
X-API-Key: tengu_...
?api_key=tengu_... query parameter.
Every FIRM response is a JSON envelope: { "ok": true, "timestamp": "<ISO-8601>", ...data }. The data keys
differ per endpoint (e.g. items for feeds, results for search, quote for a quote).
Discover every live endpoint (method, path, params) at any time — no key required:
Which products your key can call depends on your plan. Calling a product outside your plan returns
402 plan_required and charges nothing — the body's unlocked_by[] names the plans that include it.
0-credit routes (any plan):/api/v3/private_markets/search — charges nothing, but like every
/api/* data route it still requires a valid key. No-auth routes (no key needed):
/api/capabilities, /api/health, /api/status, /api/v3/monitoring/*, /api/ml/health.
À-la-carte add-ons — buy on top of any paid plan (each is its own subscription that unlocks one product +
tops your wallet): Private Markets $299/mo, Options Flow $79/mo, Copilot $199/mo. So a Starter or Pro
customer can add Copilot without going Enterprise.
Included credits/month: Free 1,000 · Starter 250,000 · Pro 2,000,000 · Expert 5,000,000 · Enterprise 20,000,000.
Rate limits: Free 30 · Starter 120 · Pro 600 · Expert 1,200 · Enterprise 6,000 req/min. See
Pricing & credits.
Many list endpoints accept ?limit (results per call) and ?offset (skip N). Defaults and maxima vary by
endpoint — the authoritative params are in GET /api/capabilities. Example:
Paths are relative to https://firm.tengu.co. {ticker} is a symbol like AAPL. This lists the most-used
routes per product; the complete set is in GET /api/capabilities (filter by tool_count/groups).
FIRM's own self-collected tick tape — minute bars, per-print options/futures trades, and a historical options chain with greeks/IV/OI. Full catalogue in Tape & Intraday History.
Institutional corporate-credit stack from licensed WRDS / S&P Capital IQ archives (served at the latest available lag). Full catalogue in Credit & Fixed-Income.
Full-text S&P Capital IQ earnings-call transcripts + the Key Developments corporate-event ledger back to 1990. Full catalogue in Transcripts & Corporate Events.
Base URL https://brain.tengu.co/v1. Auth Authorization: Bearer tengu_....
Method
Path
Shape
POST
/v1/chat/completions
OpenAI Chat Completions (model: "brain")
POST
/v1/messages
Anthropic Messages
Both support streaming (stream: true). Brain is stateless per request — send the full messages[] history to
continue a conversation. Metered per token against the shared wallet (one metered event per turn, no matter how
many FIRM tools it invoked internally). Brain requires the Enterprise plan (it has autonomous access to the
full product suite); on lower plans it returns 402 plan_required.
1{2"detail": {3"error_code": "plan_required",4"error_message": "your plan 'starter' does not include 'private_markets' — upgrade to Pro to access it. Manage your plan at https://app.tengu.co",5"tool_group": "private_markets",6"current_plan": "starter",7"unlocked_by": ["pro", "enterprise"],8"upgrade_url": "https://app.tengu.co"9 }10}
Retry policy: retry only 429 (wait Retry-After≈60s) and 502 (wait Retry-After≈5s), with exponential
backoff capped at ~120s. Never retry 401/402/403/404 — they need a new key, an upgrade, or a corrected
path. See the drop-in client in the Quickstart.