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Agent LighthouseAgent Lighthouse

    Searches the text of every published page. The evidence sources themselves are not in this index — search all of them on the trusted sources page.

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    agent-interfaces/ai-plugin-json

    ChatGPT plugin manifest (retired)

    What it checks

    Whether the site still publishes a ChatGPT plugin manifest at /.well-known/ai-plugin.json. The file is recognised by its manifest keys (schema_version, name_for_model, description_for_model, name_for_human). The scan already fetches the path, so the check costs no extra request.

    The check never asks a site to publish the file. It exists to tell an owner who still publishes it that the format is retired.

    State Result
    a JSON object with at least one plugin-manifest key warn, priority low
    no response, a non-200, an HTML page, an empty body, a body that is not JSON, or JSON without manifest keys notApplicable

    Why it matters

    Mechanism: ChatGPT read /.well-known/ai-plugin.json to install third-party plugins during the 2023 plugins beta. The claim this audit tests is the reverse: that nothing reads the file today, so a site that still publishes it maintains a file with no reader.

    Evidence

    • OpenAI closed the plugin store: “On March 19, 2024, you will no longer be able to install new plugins or create new conversations with existing plugins. You will be able to continue existing conversations until April 9, 2024.” — OpenAI Developer Community (verified 2026-10-18)
    • OpenAI’s openai/plugins-quickstart repository is archived, and its README says plugins “have been superseded by GPTs” — GitHub (verified 2026-10-18)
    • OpenAI’s current extension surface for ChatGPT apps is built on MCP, and its Actions take an OpenAPI document the developer supplies. Neither reads the manifest.
    • The path is not in the IANA Well-Known URIs registry.

    Limits

    Microsoft announced in May 2023 that it would “adopt the same open plugin standard that OpenAI introduced for ChatGPT”, across Bing and its copilots — Microsoft Build 2023 (verified 2026-10-18). So a second vendor once adopted the format. No current Microsoft documentation of reading the file was found, so the audit says no current vendor reads it. The OpenAI help-centre article on winding down the beta returns HTTP 403 to scripts, so it is cited but not used as proof. The community post and the archived repository carry the claim.

    How it scores

    Grade: D — the only documented consumer, ChatGPT plugins, was shut down by its operator. Microsoft announced adoption in 2023, but no vendor documents reading the format today. An obsolete audit carries weight 0 and never returns fail (sunset.test.ts; Audit.toCheckResult lowers a stray fail to warn). It does not move any score.

    Example finding

    /.well-known/ai-plugin.json serves {"schema_version":"v1","name_for_model":"site",…}. The report says the manifest is retired, that no client reads it, and that an MCP server declared through a Server Card is the current route.

    Sources