PayAI x402 Facilitator

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

The description conveys a read-only aggregation behavior and names the content areas (catalog size, payment volume), but with no annotations and no output schema it leaves the response structure and the precise meaning of 'settlement activity' unspecified. It is clear enough for basic selection but does not fully disclose behavioral details.

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?

Two sentences, both informative: the first states what the tool returns, the second states when to use it and why. No filler, no redundancy, and the core purpose is front-loaded.

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 parameterless tool, the description gives enough context for an agent to decide when to invoke it: aggregate stats over individual resources. It does not describe the output structure, but the summary nature is clearly conveyed. A small gap remains around exact returned metrics.

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 and schema coverage is trivially complete, so there is no parameter detail the description needs to add. The baseline of 4 applies, and the description adds no irrelevant parameter information.

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 uses a specific verb ('Returns') and names the exact resource ('PayAI Bazaar catalog') and scope ('aggregate statistics... settlement activity'). It explicitly contrasts itself with individual-resource operations, distinguishing it from siblings like list_discovery_resources without ambiguity.

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 an explicit use case ('Use it for a compact view...') and an explicit when-not-to-use ('rather than individual resources'). This directly steers an agent toward this tool for summary-level insights and away from resource-level 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, the description carries the full behavioral disclosure burden. It communicates that the tool returns live capability data and implies a read-only operation via 'Returns,' but it does not explicitly disclose whether there are any side effects, authentication requirements, or response characteristics beyond the returned data types.

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?

Two sentences with no redundant wording. The first sentence front-loads the core return value, and the second adds a practical usage hint. Both sentences earn their place.

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 no-parameter, read-only capability query, the description covers the essential information: what to expect in the response and when to use it. The lack of an output schema is partially mitigated by the explicit list of returned item types, though a note about response structure would make it fully complete.

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, and the schema is trivially complete with 100% coverage. Per the rubric, a zero-parameter tool gets a baseline of 4; the description appropriately focuses on return values rather than parameters.

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 explicitly states the operation ('Returns') and the precise resource: the payment networks, schemes, assets, and facilitator addresses currently supported by PayAI. It is specific enough to distinguish this from sibling tools like settle_payment and verify_payment, which are action-oriented, and even from list_discovery_resources, which implies a different kind of resource.

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 provides a clear usage context: 'Use it before constructing payment requirements when you need live capability data.' This tells the agent when to invoke it, though it does not explicitly state when not to use it or name alternative tools for exclusion.

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, the description carries the full disclosure burden. It signals a read-only listing operation with 'Lists' and advertises pagination via limit/offset, but it does not disclose what happens when parameters are omitted, whether a default page size applies, or any authentication/rate-limit constraints.

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?

Two short sentences with the core purpose front-loaded and no filler. The pagination guidance earns its place and nothing is 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?

Adequate for a simple list tool: it covers the operation, resource scope, item types, and pagination. However, because there is no output schema or annotations, it omits the response shape and default behavior when limit/offset are not supplied.

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%, so the description must supply meaning for limit and offset. It does so by saying to use them to 'page through' the resource list, which conveys pagination semantics, though it leaves exact conventions like skip count vs page number and defaults to the agent's prior knowledge.

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 states a clear verb and object: 'Lists' + 'x402-payable resources published in the PayAI Bazaar catalog.' It also enumerates the item types (APIs, MCP tools, agent services), and this listing operation is distinct from the sibling stats and payment tools, so an agent can confidently tell what it does.

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 does not contrast this tool with siblings or state explicit conditions for when to choose it over get_discovery_stats or get_supported. It only provides an implicit usage context (browsing discovery resources) and pagination instructions, so when-to-use vs alternatives 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.

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

With no annotations provided, the description carries the full burden, and it delivers important behavioral context: it is idempotent per signed payload, moves real funds, and specifies how to handle a pending settlement. This is strong disclosure, though it omits details like return values, authorization requirements, or irreversible consequences beyond 'moves real funds.'

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 two sentences long, front-loaded with the primary purpose and followed by the most important operational caveat. Every sentence earns its place: the first states what the tool does and its idempotency, the second explains the retry behavior.

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 that this tool moves real funds, has no output schema, and has four parameters with zero schema coverage, the description provides enough for basic invocation but leaves gaps: it does not explain what the settlement result looks like beyond an errorReason, nor does it clarify prerequisites or contrast with verify_payment. It is adequate but not fully complete for safe autonomous use.

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 input schema has 0% description coverage, and the description does not compensate by explaining what paymentPayload, paymentRequirements, x402Version, or serverExtensions mean. It references 'signed payload' and 'identical arguments,' but an agent still lacks enough information to construct valid parameter values for these opaque nested objects.

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: broadcasting a signed x402 payment on-chain and moving real funds. It is specific enough to distinguish from sibling verification tools by emphasizing actual settlement, though it does not explicitly name a sibling for contrast.

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 gives clear operational guidance, particularly the polling instruction for errorReason 'settlement_pending' and the admonition to resubmit identical arguments. It does not explicitly explain when to prefer this tool over verify_payment, but the purpose of moving funds implies the settlement use case.

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 it does disclose the key behavioral trait that no funds are moved, which meaningfully clarifies this is a safe, non-mutating verification. Yet it omits other behavior agents would need: what happens on an invalid payload, whether the call ever throws or returns a failure signal, and what the return value conveys about validity.

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?

Two concise sentences with zero filler. The first states the primary action and target; the second adds the critical non-mutating behavioral clarification. Both sentences earn their place, and the most decision-relevant clause ('moves no funds') is placed at the end as a deliberate contrast rather than buried.

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?

The definition captures the key verification vs. fund-movement distinction, which is essential for an agent picking between this and settle_payment. However, with no output schema, two undocumented nested object parameters, and 0% schema coverage, the description leaves an agent uncertain about what the call returns on valid vs. invalid payments and what format the requirements must take.

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%, so the description must compensate. It maps two of the four parameters — paymentPayload ('payment payload') and paymentRequirements ('payment requirements') — but gives no meaning to x402Version despite it being the only parameter with a documented enum, and says nothing about serverExtensions. Nested objects further raise the burden, and the description only partially meets it.

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 states a specific verb (verifies) and a clear resource (signed x402 payment payload), and frames the action against 'supplied payment requirements.' It does not explicitly name sibling settle_payment, but the 'moves no funds' clause implicitly distinguishes it from the fund-transfer sibling, which earns most of the differentiation credit but not the explicit clarity of a named alternative.

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 phrase 'it checks validity but moves no funds' gives implied usage context, signaling this is a verification-only operation and implying that fund movement belongs to a sibling like settle_payment. However, no sibling is named, no when-to-use vs when-not-to-use is spelled out, and there is no mention of prerequisites such as the requirements being already settled.

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