402Signal MCP Server

Use preview first when you need to discover paid APIs by capability without paying or contacting seller endpoints. It searches upstream catalogs plus the local catalog; returned claims and any earlier observations are not a new live check (not_probed=true). The freshness timestamp describes this search response, not when each seller was last probed. Results can be limited or non-exhaustive. Pass a nonblank need describing the capability, not a URL to test. Omit networks to search all supported rails; an empty list searches none. networks is a hard allowlist; prefer_network only ranks results and cannot add an excluded rail. A chain mentioned in need can influence ranking when prefer_network is omitted. Use validate next for an unpaid readiness check of one concrete catalog-listed URL. Use route instead when you need fresh selection against price, network or readiness rules, or signed routing evidence. Preview does not enforce a purchase budget, reserve a price or authorize payment.

Use route when you need a live paid-API selection that satisfies spending and readiness rules. Use preview instead for free catalog discovery without probing, or validate for a free readiness check of one catalog-listed URL without constraint-based selection or signed routing evidence. Route does not buy the seller's service. Start with need (a capability such as weather), or url (one concrete HTTPS endpoint). If both are supplied, url selects the endpoint; need can still supply policy context. Add only the rules you require: networks is a hard allowlist, while prefer_network only ranks within it. Omit networks for all supported rails; [] permits none. objective defaults to best among eligible candidates actually probed. search_depth defaults to standard; max_candidates_to_probe sets a ceiling capped at 20, not a promise to probe that many. Direct URL requests check one endpoint. Price bounds concern the seller, not the separate routing fee: max_price_usd bounds its price; max_total_cost_usd also requires known fees. Required unknown price, latency or history measurements fail the constraint. max_probe_latency_ms takes precedence over its max_latency_ms alias; neither is service latency nor settlement latency. Structured constraints override constraints interpreted from policy (or need when policy is absent); inspect unresolved_constraints rather than assuming prose was enforced. For buyer-side comparison before merchant signing, set require_route_binding=true; it also requires transparency even if require_transparency=false. The hosted check may then select the next already-probed selectable candidate that can bind; it does not settle an unguarded winner. HTTP 503 route_binding_unavailable means none remained bindable. A later expired or changed seller offer does not reverse an already settled routing fee. The first unsigned call returns an HTTP 402 routing-fee challenge; completing it requires an x402-capable HTTP client, not a wallet key or payment argument. The credential-free Glama stdio adapter cannot complete paid route calls. The $0.003 USDC routing fee settles only for a qualifying live result; completed misses are not settled. Inspect billing, not just HTTP status; on an unknown outcome stop and reconcile rather than creating another authorization. MCP does not provide recovery-only requests. Seller payment remains separate.

Use validate for an unpaid readiness check of one concrete HTTPS seller endpoint already listed in the local catalog, for example a URL returned by preview. It compares claimed and observed payment/readiness information and returns flags; it does not purchase the service or add a routing observation to history. Supply the exact listed URL, including its query string. The URL must be nonblank HTTPS; private/local destinations and unresolved path templates are refused. An unknown or modified URL can return miss_reason=no_candidates without any seller probe; this means not listed, not proven offline. Inspect live, readiness, observed and miss_reason rather than treating HTTP 200 as success. Use preview instead to find endpoints by capability. Use route for live constraint-based selection or signed routing evidence, including when you need to evaluate a direct URL outside the catalog subject to routing safety checks. Validate has no price or network filter, produces no signed route receipt, and is not proof that a paid call will deliver the desired result.