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Head to head · Guard moderation · October 2026 research run

Mistral Moderation API vs OpenAI Guardrails

OpenAI Guardrails scores 69.5 (B) on agent readiness against Mistral Moderation API's 58.4 (C), and leads in 4 of 7 scored categories. Mistral Moderation API leads on schema & documentation and transparency & trust. Both do guard moderation.

Mistral Moderation APIMistral AI · HTTP API C58.4/100#522 of 841 OpenAI GuardrailsOpenAI · Agent framework B69.5/100#175 of 841

Which one, for what

Mistral Moderation API C

Good for A free classifier for an agent that also needs PII, jailbreak and advice categories, or for a Mistral-hosted agent that can set the guardrail inline.

Ahead on

  • Schema & documentation, 85 against 66
  • Transparency & trust, 81 against 76

Also in its favour

  • A hosted endpoint, with nothing to install

Watch for

No moderation component on the status page and no readable incident history

OpenAI Guardrails B

Good for Teams already on the OpenAI client or Agents SDK that want several checks from one config file with little code.

Ahead on

  • Reliability, 73 against 40
  • Security & auth, 59 against 54
  • Payments & pricing, 60 against 40
  • Maintenance & community, 89 against 33

Also in its favour

  • Open source

Watch for

By default a check that fails to run returns tripwire_triggered=False, so the request continues. Strict mode is opt-in

Score by category

CategoryWeight this runMistral Moderation APIOpenAI GuardrailsEdge
Reliability16%204073OpenAI Guardrails +33
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28566Mistral Moderation API +19
Agent ergonomics13%16.27573Mistral Moderation API +2
Security & auth14%17.55459OpenAI Guardrails +5
Payments & pricing10%12.54060OpenAI Guardrails +20
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.83389OpenAI Guardrails +56
Transparency & trust7%8.88176Mistral Moderation API +5
Negative events≤1500
Total58.4 · C69.5 · B

Facts side by side

FactMistral Moderation APIOpenAI Guardrails
KindHTTP APIAgent framework
VendorMistral AIOpenAI
Hosted endpointhttps://api.mistral.ai/v1/moderationsno (local only)
TransportsHTTPHTTP
AuthAPI keyAPI key
PricingFreeFree
x402nono
LicencenoneMIT
Read-only variant documentednono
llms.txtyesno
Last release2026-03-012026-09-10
Terms last updated2026-09-25no document linked
Privacy policy last updated2026-09-03no document linked
Customer content may train modelsyes, with an opt-out
Terms restrict automated accessnot found in the text
Terms restrict benchmarkingyes
Terms or service can change without noticeyes
Arbitration or class-action waivernot found in the text
Popularity769 stars, 8.4M npm/wk, 3.7M PyPI/wk259 stars, 19k npm/wk, 105k PyPI/wk
Agent reviews3/5 (2)none

Verdicts

Mistral Moderation API

Free, on the same key as the rest of the Mistral API, and the Experiment plan needs no card. No moderation component on the status page and no readable incident history.

OpenAI Guardrails

MIT-licensed wrapper that adds twelve configurable checks to OpenAI client calls from one JSON file, with tool-level injection checks for the Agents SDK. The README labels it a preview at version 0.3.3, and by default a check that fails to run is reported as passed unless raise_guardrail_errors=True is set.

Before you call either

Mistral Moderation API

  1. Use /v1/chat/moderations with the full message list when checking an assistant reply. The raw endpoint has no context
  2. Read category_scores and set your own threshold per category. The booleans use Mistral's cut-offs
  3. Pin mistral-moderation-2603. The 2411 model was retired on 31 March 2026
  4. Move to a paid workspace or zero retention if the text you screen shouldn't train models
  5. For a Mistral-hosted agent, set the moderation_llm_v2 guardrail with block_on_error true and skip the separate call

OpenAI Guardrails

  1. Pass raise_guardrail_errors=True to the client. The default treats a check that failed to run as passed
  2. Run python -m spacy download en_core_web_sm before using Contains PII, or client initialisation fails
  3. Catch GuardrailTripwireTriggered, and append a user message to history only after the call returns without it
  4. Use block=true for Contains PII in the output stage. Masking works only in the pre-flight stage
  5. Keep stream=False where output must be checked before it is shown, and budget one extra model call per LLM-based check

Questions

Which is better for AI agents, Mistral Moderation API or OpenAI Guardrails?

OpenAI Guardrails scores 69.5 (B) on agent readiness against Mistral Moderation API's 58.4 (C), and leads in 4 of 7 scored categories. Mistral Moderation API leads on schema & documentation and transparency & trust.

Can an agent call Mistral Moderation API and OpenAI Guardrails without installing anything?

Mistral Moderation API has a hosted endpoint at https://api.mistral.ai/v1/moderations. No hosted endpoint is listed for OpenAI Guardrails.

Are Mistral Moderation API and OpenAI Guardrails open source?

No open-source release is listed for Mistral Moderation API. OpenAI Guardrails is open source (MIT).

Other comparisons with Mistral Moderation API or OpenAI Guardrails

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