A2Agent compatibility testing: custom vision endpoint configuration #28

Hi openplate maintainers,

I represent A2Agent, an OpenAI- and Anthropic-compatible API gateway. We'd like to verify compatibility with your existing provider configuration and contribute a focused PR.

Your existing OpenAI-compatible vision adapter is the right integration point. We would like to document and test custom API-root normalization together with the existing structured-output fallback.

• A placeholder-key custom vision-endpoint example with explicit model capability requirements.
• Offline request-path fixtures for trailing-slash variants and structured-output fallback.
• Checks that authentication, quota, payload-size, and rate-limit errors do not cause redundant image uploads; no real user photos in fixtures.

Would you prefer a documentation/test-only PR or a broader integration?

Separately, after successful verification, would you consider including A2Agent wherever you document tested providers? We'll follow your preferred wording and placement, without implying endorsement.

We can privately provide a test key with US$10 in one-time API credits, plus technical support. This support is not conditional on merging, endorsement, or listing.

Thanks!