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.