Search for MCP tools by capability. Each result is one (product, tool) pair — tools sharing a name across providers are NOT interchangeable, so each provider's tool is its own row with its own description and input schema. Ranking basis: semantic relevance to the query (embedding search); on the lexical fallback (searchMode='lexical') results are name-ordered and rank does NOT reflect relevance. Paid tier is NOT a ranking input — it appears only as an annotation. Every result carries { position (1-based), rank (0..1; 1.0 = top) } so callers can merge results across tools consistently, plus preflight annotations { accessModel (open|keyed|account|commercial; whether an agent can call it without becoming a customer first), healthScore (0-100, nullable), readOnly, destructive } so you can judge callability and safety BEFORE selecting. Optional access filter narrows to a single access class. Response: { searchMode ('semantic'|'lexical'), tools: [{ position, rank, normalizedName, displayName, description, inputSchema, productSlug, productName, serverQualifiedName, isRemoteCapable, accessModel, healthScore, readOnly, destructive, tier, unverified (true when no approved vendor claim), verifiedAt (ISO; nullable) }] }. Errors: { error: { code: 'bad_input', ... } }.