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

With no annotations, the description carries the full burden and succeeds. It discloses that the call is 'PUBLIC: needs no API key, no wallet and spends nothing, so it is always safe to call,' and warns that `amount` is in ATOMIC units (with a conversion example). These are behavioral traits beyond what the schema/annotations convey, essential for an agent to safely invoke the tool.

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

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

The description is moderately long but each sentence earns its place: purpose, sibling differentiation, return structure, atomic-unit caveat, safety, and filtering/pagination guidance. It is front-loaded with the main purpose and flows logically. No redundancy or filler.

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

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

Given the absence of an output schema, the description fully compensates by detailing the return shape ({ resources: [...], pagination: {...} }), explaining atomic unit conversion, and noting safety. It also covers filtering and pagination usage. For a moderately complex tool with no annotations or output schema, this description is comprehensive enough for correct selection and invocation.

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

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

Schema coverage is 100%, so the baseline is 3. The description mentions 'Filter with `type` (e.g. "http") and page with `limit`/`offset`,' but this largely restates the schema descriptions and adds minimal new meaning. It does contextualize parameters in the workflow, but doesn't go beyond what the schema already provides, so it remains at baseline.

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

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

The description clearly states the tool's purpose: 'Discover x402-gated APIs you can pay for — browse the facilitator's Bazaar catalogue of registered x402 resources.' It uses a specific verb ('Discover') and resource, and explicitly distinguishes from its sibling x402_pay by noting that the pay tool only fetches a URL you already have, making this the only way to locate a paid endpoint independently.

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

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

It gives explicit guidance: 'Use this BEFORE x402_pay whenever you need to FIND a paid endpoint rather than call one you were already given.' It also provides follow-up direction ('Then pass a chosen `resource` URL to x402_pay') and clarifies exclusions (when you already have a URL, use pay instead). This fully covers when-to-use and alternatives.

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

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

With no annotations provided, the description carries the full burden and does so well: it details the 402 sequence (parse price, authorize, sign locally non-custodially, retry with X-PAYMENT), the return shape {status, paid, body, settlement?}, supported vs upcoming chains, the exact behavior on unsupported families (family_not_yet_supported), clean error handling for unconfigured keys, and a security warning about holding spending keys.

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

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

Purpose and 402 behavior are strongly front-loaded, followed by alternatives, chain support, config, and security in a logical order. It is long for a description, and the SECURITY warnings and env-var reiterations appear twice, so a small amount of trimming is possible.

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

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

Despite 16 parameters, no output schema, and no annotations, the description covers what an agent needs: the return shape, the payment flow, supported/upcoming networks, error semantics, required configuration, and safety controls. Nothing material for correct invocation is missing.

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

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

Schema description coverage is 100%, so the baseline is 3. The description goes beyond the schema by framing allowedNetworks, maxAmount, and allowedHosts as a coherent safety posture, explaining that env-pinning keeps the allowlist outside the model's reach, and describing the CRYPTOAPIS_API_KEY/X402_WALLET_ID setup once. This adds genuine framing value, though much of the per-parameter detail is already in the schema.

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

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

States a specific verb (fetch) and resource (HTTP resource), then specifies the conditional behavior (pay on 402 and return the paid response). It explicitly distinguishes itself from the sibling x402_pay_tool (HTTP URLs vs paid MCP tools), so an agent can route without opening either schema.

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

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

Explicitly names the alternative (x402_pay_tool for paid MCP tools on another server) and the condition that selects it. It also gives when-to-use guidance for the safety controls (allowedNetworks, maxAmount, allowedHosts) and the trusted-local-environment precondition for holding spending keys.

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

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

No annotations are provided, so the description carries the full burden — and it does: it discloses the challenge/retry flow, non-custodial local signing ('the key never leaves this process'), where PaymentRequired is read from (structuredContent with content[0].text fallback), that the upstream server is launched over stdio and shut down per call, supported vs coming-soon chains, and an explicit SECURITY warning about holding spending keys.

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

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

Dense but every sentence earns its place — flow, return shape, credentials, supported chains, and security are all load-bearing for a 14-parameter tool. Slightly over-packed with parentheticals, but front-loaded and non-redundant.

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

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

With no output schema present, the description supplies the return contract ('{ paid, result, settlement? }') and where the settlement receipt arrives (_meta['x402/payment-response']), plus credential and network coverage. Given the tool's complexity and nested server object, an agent has everything needed to call it correctly.

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

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

Schema coverage is 100%, so the baseline is 3 and the schema already documents fallbacks and formats. The description adds meaning on top by naming the credential set (CRYPTOAPIS_API_KEY, X402_WALLET_ID, X402_PRIVATE_KEY/X402_SVM_SECRET) and framing allowedNetworks/maxAmount as guardrails, which tells the agent how to use them defensively.

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

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

States a specific verb+resource ('call a tool on another MCP server and pay it automatically with x402') and explicitly positions itself against the sibling x402_pay ('MCP-transport twin... use x402_pay for an HTTP url, and THIS for a paid tool on another MCP server'). An agent can unambiguously separate it from x402_pay and x402_discover.

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

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

Gives an explicit selection rule against the closest alternative and a clear exclusion ('use x402_pay for an HTTP url'), plus a security scoping condition ('use only in trusted local environments'). Nothing about when-to-use 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.