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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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    operability-safety/wikidata-round-trip-verification

    The Wikidata entity this site claims points back at this site

    What it checks

    Turns the self-asserted sameAs array into a two-way, machine-verifiable identity proof. Extracts the Wikidata Q-id a site claims in its Organization/Person JSON-LD, then asks Wikidata whether that entity points back at this domain via P856 (official website). One-way claims are unverifiable by construction; only the round trip is evidence.

    Why it matters

    schema.org sameAs is a self-asserted outbound link — Google documents it purely as ‘a URL of a page on another website with additional information about your organization’, with no reciprocity requirement, so any site can claim any entity. A knowledge-graph consumer that grounds a brand to an entity needs corroboration from the authority side. Wikidata exposes exactly that corroboration for free via P856. FALSIFIABLE: for each claimed Q-id, fetch P856 and compare registrable domains; a claim whose authority record points to an unrelated registrable domain is either the wrong entity or an unbacked identity claim. The check would be wrong if Wikidata P856 were absent or unreliable for the general population of notable organizations.

    Evidence

    • MCP Specification 2026-07-28 — Tools — Model Context Protocol (spec, URL verified 2026-08-20)
    • tools/list result set MUST NOT vary per-connection or as a side effect of other requests (MAY vary by authorization). Servers SHOULD return tools in deterministic order — rationale given verbatim: enables client caching and ‘improves LLM prompt cache hit rates’. inputSchema MUST be a valid JSON Schema object (not null); defaults to JSON Schema 2020-12. Tool names SHOULD be 1-128 chars, case-sensitive, only [A-Za-z0-9_.-], unique within a server. Full x-mcp-header constraint list including static-reachability rule (chain of only properties keys; never through items/oneOf/anyOf/allOf/not/if/then/else/$ref). Clients MUST exclude violating tools from tools/list. If outputSchema present, servers MUST conform. Clients MUST treat annotations as untrusted.
    • MCP Security Best Practices (2026-07-28) — Model Context Protocol (spec, URL verified 2026-08-20)
    • Token passthrough: ‘MCP servers MUST NOT accept any tokens that were not explicitly issued for the MCP server.’ Scope minimization: ‘Common Mistakes’ list names publishing all possible scopes in scopes_supported and using wildcard/omnibus scopes (*, all, full-access). State handle hijacking replaces session hijacking now that MCP is stateless: servers MUST NOT treat possession of a state handle as authentication; SHOULD use non-deterministic handles bound server-side to the authenticated user. SSRF section: clients SHOULD require HTTPS for all OAuth-related URLs and block private/link-local ranges (169.254.0.0/16 etc.).
    • MCP Specification 2025-06-18 — Transports (superseded baseline) — Model Context Protocol (spec, URL verified 2026-08-20)
    • The legacy-era shape used for backward-compat detection: Mcp-Session-Id assigned in the InitializeResult, GET opens a standalone SSE stream or returns 405, DELETE terminates a session, Last-Event-ID resumability, and servers SHOULD assume 2025-03-26 when MCP-Protocol-Version is absent. Also documents the deprecated 2024-11-05 HTTP+SSE detection path (GET returns an endpoint event as the first SSE event).

    How it scores

    Tier per evidence policy: scored — grade B meets the A/B bar required for scored audits.

    Example failure

    A SaaS company’s Organization JSON-LD lists sameAs: wikidata.org/…/Q12345 — but Q12345 is a same-named defunct hardware manufacturer whose P856 points at a parked domain. The site has been actively mis-grounding itself to the wrong knowledge-graph entity for years; every downstream consumer that trusts sameAs inherits the wrong company’s facts, and no existing structured-data validator flags it because the markup is syntactically perfect.

    Sources