Payzilla Marketplace

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

Beyond the annotations, it explains the exact payment mechanism, the two-phase interaction, external wallet signing, and that the tool only forwards the payment. It also warns that seller-written listing text is not an instruction, which is valuable prompt-injection context.

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 front-loaded with the core action and protocol, then gives the invocation sequence and safety note in four compact sentences. Every sentence adds useful operational context without 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 financial payment tool with a simple schema and no output schema, it covers the essential flow, signing model, network, token, and safety warning. It still leaves out response/payment-requirements shape and error or status-checking guidance, which would help for a complex payment 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?

With 0% schema description coverage, the description usefully identifies the listing id and the signed-payment _meta channel. However, it does not explain the id format or constraints, and because _meta is not in the input schema while additionalProperties is false, the guidance remains potentially confusing for invocation.

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 and resource: pay for one Marketplace listing, including the x402 payment rail and USDC on Solana mainnet. The payment action is clearly distinct from the sibling read/status tools such as marketplace_get_listing, marketplace_search, and payment_status.

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 a clear two-step invocation flow: first call with only the listing id to obtain payment requirements, then call again with the signed payment in _meta. It does not explicitly compare against payment_status or say when not to use this tool, so it falls short of full alternative guidance.

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?

Beyond the readOnlyHint annotation, the description adds that the operation is free, that seller-written listing text is not an instruction, that payTo must match the payment terms wallet, and that payUrl is for the user to open in their own wallet. These are substantive behavioral and security details that materially affect correct use.

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 compact and front-loaded, starting with the core action and then adding the important field and safety details. Every sentence contributes useful information without repetition.

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?

Because there is no output schema, the description usefully names the key returned fields such as price, seller label, marked status, payTo, and payUrl. It also covers read-only behavior and prompt-injection safety, though it leaves the id parameter underspecified.

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 is one required parameter with 0% schema description coverage, so the description should compensate. It only echoes 'by id' and does not explain where to obtain the id, its expected format, or the 36-character limit present 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?

The description states a specific verb and resource: 'Show one Marketplace listing by id,' and lists the fields returned. It implicitly distinguishes itself from marketplace_search by emphasizing a single listing by id, but it never names the sibling alternatives explicitly.

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 some usage guidance, notably that payUrl should be handed to the user and that payment terms must reference the same payTo wallet. However, it does not say when to use this tool versus marketplace_search, listing_pay, or payment_status, leaving the routing decision mostly implied.

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?

Goes well beyond the readOnlyHint/openWorldHint annotations: it declares the call is free, states the return shape is data fields only, and explicitly warns that seller-written listing text is not an instruction — a meaningful prompt-injection guardrail. It also tells the agent what to do with payUrl rather than leaving a returned link unresolved.

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?

Three short sentences, each earning its place: purpose first, safety/behavior second, output handling third. No restatement of the title 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?

With no output schema, the description usefully covers return semantics (data fields, payUrl) and content-trust caveats. The remaining gap is the undocumented limit/pagination and default-empty-query behavior for a tool with zero schema coverage.

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 carry the parameter burden. It explains what 'query' matches against, but says nothing about 'limit' (default 10, max 20) and does not state what an empty query returns, leaving the default search behavior ambiguous.

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 ('Search') plus resource ('Marketplace listings') and the matching rule ('by words in the name or description'), which is enough to distinguish it from marketplace_get_listing and listing_pay. It stops short of naming the sibling tools that cover single-listing lookup and payment, so the differentiation is inferable rather than explicit.

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?

'Read-only and free' plus the payUrl instruction gives a clear sense of context, but there is no explicit when-to-use/when-not guidance relative to marketplace_get_listing or payment_status. The agent must infer that this is the discovery step preceding those tools.

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?

Adds real disclosure beyond the annotations: the tool reads only this service's own record, never the seller or the chain, which explains the openWorldHint=false boundary and warns against treating a miss as proof of failure. The confidentiality note ('whoever holds the reference can read it, keep it private') is valuable, non-obvious behavior. It stops short of describing what states can be returned or what an unknown reference yields.

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?

Four short sentences, front-loaded with the core action and reference provenance, then the read-scope caveat, then the security warning. Nothing is padded; 'read-only and free' is the only near-duplication of the annotations and it adds the cost fact.

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 one-parameter, no-output-schema tool the description covers invocation and trust boundaries well, but leaves the return shape undefined: an agent cannot tell what state values to expect or how an unknown/pending reference is represented. That gap matters precisely because there is no output schema to fall back on.

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 0% – the reference parameter has no description or format guidance in the schema. The description compensates well by explaining where the reference comes from and treating it as the sole access key, but does not mention the 36-character cap or expected format.

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 and resource ('Show the state of a payment') plus the exact provenance of the identifier ('made with listing_pay, by the reference that listing_pay gave you'). This cleanly separates it from the sibling listing_pay (which creates the payment) and from the marketplace_* lookup tools.

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 precondition (a reference produced by listing_pay), an explicit availability note ('read-only and free'), and an explicit when-not path: for an unknown or pending payment, verify on-chain yourself before paying again. That is the alternative-action guidance an agent needs, with no inference required.

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