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Semantic search over the x402 catalog (paid)

x402_semantic_search

Find candidate x402 endpoints by plain-language capability query, ranked by semantic similarity and trust score, before inspecting them in depth.

Instructions

Free-text SEMANTIC SEARCH across the entire monitored x402 endpoint catalog. Given a plain-language query (e.g. "weather forecast", "image generation", "EVM gas price oracle"), returns the up to 25 endpoints whose advertised purpose is semantically closest. Ranking is deterministic and fully specified: cosine similarity bucketed to whole percentage points first (80.3% and 80.5% are the same bucket, so sub-percent noise never outranks a better endpoint), then trust score (0-100), then described-before-undescribed, then endpoint id as a stable final tiebreak. Matches below a 0.5 cosine-similarity floor are dropped entirely, so a query can return fewer than the requested limit (or none). Endpoints that advertise no description are still matched: they are embedded from their service name and URL path tokens instead of a written description (host name as a last resort). The EXACT effect of a missing description: no fixed point deduction, and no direct similarity malus either; the only deterministic penalty is the described-before-undescribed tiebreak (at equal similarity bucket AND equal trust score, a described endpoint ranks first). Beyond that the effect is purely indirect: the shorter fallback text typically yields lower cosine similarity than a prose description, so undescribed endpoints tend to land in lower similarity buckets, by a query-dependent (never fixed) amount. Use this for DISCOVERY: find candidate endpoints for a capability before checking any of them in depth. Each match carries 'id', 'resource' URL, trust 'score' (0-100), 'grade' (A-F), raw cosine 'similarity' (0-1; ranking buckets it to whole percents), 'amountUsd' price (null when not advertised), 'priceCeiling' (true when amountUsd is an x402 'upto' authorization ceiling, not a fixed per-call price), 'description' when advertised, and a free 'endpointPage' URL. 'score'/'grade' are null for endpoints not yet scored. Deliberately NO verdict/recommendation or flag detail: the per-endpoint trust report (x402_trust_score) carries those. Pay-per-call over x402 (~$0.001); auto-pays if a wallet is configured, otherwise returns the price quote.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
limitNoMax matches to return (1-25, default 25)
queryYesFree-text search query, e.g. "weather forecast". Describe the capability you need in plain words; matching is by meaning, not substrings.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv1.11.2

TDQS

A4.8/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full behavioral burden and does so thoroughly: pay-per-call pricing (~$0.001), auto-pay when a wallet is configured versus returning a price quote, the deterministic ranking order with tiebreaks, the 0.5 cosine floor that can return fewer than the requested limit, and the exact treatment of undescribed endpoints. It even discloses what is deliberately omitted from results.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Purpose and routing are front-loaded in the first sentence, and the output-field inventory and pricing note are dense but useful. The paragraph detailing missing-description effects is noticeably verbose and repeats the same point (no fixed penalty, only indirect similarity effect), which keeps it from a 5.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, so the description enumerates the returned fields (id, resource, score, grade, similarity, amountUsd, priceCeiling, description, endpointPage) and their nullability. Combined with the pricing/auth behavior and ranking rules, an agent has everything needed to invoke the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the schema already documents both parameters (baseline 3). The description adds meaning beyond it: matching is by meaning not substrings (reinforcing the query param), the top-N cap of 25, and the important behavioral note that a query can return fewer than the requested limit.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (semantic free-text search across the monitored x402 endpoint catalog) and frames the scope precisely. It explicitly distinguishes itself from the trust-report siblings by naming x402_trust_score for verdicts/recommendations, so an agent can tell the tools apart without opening a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit when-to-use guidance ("Use this for DISCOVERY: find candidate endpoints for a capability before checking any of them in depth") and a when-not/alternative condition (per-endpoint trust report via x402_trust_score carries verdicts and flag detail). Nothing needed for routing is left to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.