x402 Pay — USDC API Payment Helper

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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds valuable behavioral specifics: it performs a live inspection of a URL, targets x402 challenges, and explicitly avoids sending payment. It does not detail network behavior or response characteristics, but the annotation coverage lowers the burden.

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 a single, front-loaded sentence with no filler. Every word contributes meaning: 'inspect,' 'HTTPS URL,' 'live x402 402 challenge,' and 'without sending payment' all add operational value.

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?

For a low-complexity, one-parameter read-only tool, the description covers the essential context: what URL to provide, what to check for, and what side effects are intentionally avoided. It does not explicitly describe the return value, but the absence of an output schema is mitigated by the simplicity of the operation.

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?

The schema only defines 'url' as a string with length constraints, and schema description coverage is 0%. The description compensates by specifying that the URL must be an HTTPS URL and that it is inspected for a live x402 challenge. For a single simple parameter this is sufficient semantic guidance.

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 a specific action: inspecting an HTTPS URL for a live x402 402 challenge. It also adds the key differentiator 'without sending payment,' which separates it from payment execution tools and clarifies its scope.

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?

The description makes the intended use clear: check whether a URL currently presents an x402 challenge before any payment is sent. It does not explicitly name sibling tools or give when-not-to-use conditions, but the context is specific enough for an agent to understand when this check is appropriate.

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?

Annotations already declare the tool read-only, idempotent, open-world, and non-destructive, so the bar for additional disclosure is lower. The description adds only a resource qualifier ('live always-on'), which hints at current liveness, but it does not describe output, failure behavior, or any other runtime traits.

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 a single short sentence with the verb and resource front-loaded. It is compact, though 'live' and 'always-on' are somewhat redundant, so it is not perfectly economical.

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, the description does not clarify what the returned status contains, and 'payment authority' is left as an unexplained domain term. However, the tool has zero parameters and strong safety annotations, so the missing context is limited mostly to expected response shape and domain meaning.

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?

There are zero parameters and schema coverage is 100%, so there is no parameter documentation burden on the description. A baseline of 4 is appropriate for a no-parameter tool.

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 action ('Check') and resource ('SqueezeOS payment authority'), with the 'live always-on' qualifier suggesting this probes current availability. It does not explicitly differentiate from sibling check_payment, but the resource naming gives it a distinct target.

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?

No guidance is given on when to use this tool versus check_payment, list_paid_apis, or payment_info. The 'always-on' phrase implies availability but provides no conditions, exclusions, or alternative-selection hints.

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?

The annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint: false, so the safety profile is covered. The description adds the useful context that the data is 'live' and comes from the 'canonical SqueezeOS OpenAPI document,' which signals authoritativeness and freshness. It does not detail response shape, pagination, or failure behavior, so some behavioral context is still missing.

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 a single, front-loaded sentence that wastes no words. It states the action, the target resource, and the source document without filler or redundant restatement of the tool name.

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?

For a simple listing tool with one optional parameter and solid safety annotations, the core purpose is adequately described. However, it lacks usage context relative to sibling tools and does not clarify what the returned 'paid API operations' look like, which leaves minor but real gaps for an agent trying to select and invoke it optimally.

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 0%, and the description does not mention the `limit` parameter at all. The schema provides type, default, minimum, and maximum, so the agent can infer basics, but the description fails to compensate for the low coverage and adds no meaning beyond 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?

The description clearly states a specific verb and resource: 'List live SML x402 paid API operations from the canonical SqueezeOS OpenAPI document.' This makes the tool's basic purpose unambiguous and distinguishes it from the check_* siblings through the 'List' action. However, it does not explicitly differentiate itself from siblings like check_payment or payment_info beyond the verb and object.

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?

There is no explicit guidance about when to use this tool versus alternatives such as check_payment, check_status, or payment_info. The description only implies that this is for discovering available paid APIs, but it never states exclusions, prerequisites, or conditions that should route an agent to a sibling tool.

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?

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds 'Never spends,' which is a domain-specific confirmation but essentially restates the read-only safety profile in payment terms. It provides no new constraints like rate limits, authorization, or response behavior beyond what annotations imply.

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 extremely concise: two short sentences. The first sentence states the purpose, and the second adds a safety guarantee. Every word earns its place, and there is no redundant or vague 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?

For a zero-parameter, read-only tool with no output schema, the description gives the essential information: what is returned and that it does not spend. It is slightly incomplete in that it does not specify the exact shape or format of the return value (e.g., what 'payment network and receiver' concretely looks like), but for this simple tool it is nearly sufficient.

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?

The tool has zero parameters, so there is no parameter ambiguity. The description does not need to explain input semantics, and the input schema already covers everything. Baseline for zero-parameter tools is 4.

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 a specific verb ('Return') and a specific resource ('canonical ScriptMasterLabs x402 payment network and receiver'). It is unambiguous about what the tool provides. However, it does not explicitly distinguish itself from sibling tools like check_payment or list_paid_apis, so it stops short of full differentiation.

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?

No guidance is given about when to use this tool versus the sibling tools (check_payment, check_status, list_paid_apis). There is no mention of contexts, exclusions, or alternatives. The word 'canonical' implies a default reference, but the description does not actively instruct an agent on selection.

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