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Helicone API

Helicone API

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Helicone API is an LLM observability tool — one-line proxy integration to trace, monitor, cache, rate-limit any OpenAI / Anthropic call.

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Use it when

Extremely simple integration (change base_url, one line)

Watch for

Proxy mode adds small latency (~50ms)

First check

Sign up at helicone.ai for API key. OpenAI SDK: client.base_url = "https://oai.helicone.ai/v1"; headers["Helicone-Auth"] = "Bearer ..."

Auth
api_key
CORS
?
HTTPS
Yes
Signup
?
Protocol
REST
Pricing
freemium

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01

About this API

Helicone is a 2023 YC LLM observability startup. Different path from LangSmith: LangSmith instruments code via SDK; Helicone uses proxy — just change OpenAI base_url to Helicone proxy URL, all LLM calls auto-trace without changing other code. This "one-line integration" is its killer feature, especially for projects not using LangChain. Function coverage: complete request trace (per-call prompt, response, cost, latency), cost dashboard, cache (same prompt auto-hits cache to save tokens), rate limit (prevent abuse), user-level analytics, A/B testing prompt versions. Open-source (Apache 2.0), self-hostable. Smaller ecosystem than LangSmith but fast-growing, especially in startup circles.

02

What you can build

  • 1LLM app monitoring (cost / latency / error rate)
  • 2Quickly trace LLM calls for debugging
  • 3Cache repeated prompts to save cost
  • 4Rate limit to prevent abuse
03

Strengths & limitations

Strengths

  • Extremely simple integration (change base_url, one line)
  • Generous free tier 100k requests/month (more than LangSmith)
  • Supports all LLM providers (not limited to LangChain)
  • Open-source (Apache 2.0)

Limitations

  • Proxy mode adds small latency (~50ms)
  • Eval framework less complete than LangSmith
  • Ecosystem smaller than LangSmith
04

Example request

Generic template — replace <endpoint> with the real path from the docs.
curl https://www.helicone.ai/<endpoint> \
  -H "Authorization: Bearer $API_KEY"
# Some providers use X-Api-Key instead — verify in the docs.
05

Getting started

Sign up at helicone.ai for API key. OpenAI SDK: client.base_url = "https://oai.helicone.ai/v1"; headers["Helicone-Auth"] = "Bearer ..."

06

FAQ

Helicone proxy latency?+

Generally under 50ms. Global deployment + edge workers — negligible for most apps.

Can I self-host?+

Yes. Open-source (Apache 2.0), docker-compose runs locally in a few commands.

07

Technical details

CORS: ?HTTPS: YesSignup: ?Open source: No
Auth type
api_key
Pricing
freemium
Rate limit
免费 100k requests/月
Protocols
REST
SDKs
python, typescript, javascript
08

Tags

heliconellm-observabilitymonitoringai