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

With no annotations, the description explicitly discloses that calling this does not charge anything, a key behavioral trait. It also lists return fields, but does not mention error handling, authentication, or rate limits. The non-charging disclosure is valuable and goes beyond the schema, though other side effects or constraints are omitted.

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, front-loaded with the core purpose and the list of returned fields. The bundle special case is added in a second sentence without redundancy. Every word earns its place, and the structure is easy to parse.

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 there is no output schema, the description lists all the fields returned (amount, asset, network, payTo, scheme, endpoint), which is sufficient for an agent to interpret the response. It also explains the bundle special case and the non-charging behavior. Nothing critical is missing for invocation or interpretation.

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 already documents 'id' as 'Report id, or "bundle"', covering 100% of the parameter. The description adds meaning to the 'bundle' value by explaining it quotes the full-catalog bundle and calling it 'the highest-value purchase'. This extra semantic context goes beyond the bare schema, justifying a 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 states a specific verb 'Return' and the resource 'x402 payment requirements for a paid report', enumerating the exact fields (amount, asset, network, payTo, scheme, endpoint). It clearly distinguishes from siblings like buy_report (which executes a purchase) and list_catalog (which lists reports), making the tool's purpose unambiguous.

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 implies this is a quoting tool but does not explicitly contrast it with buy_report or name alternatives. The statement 'Nothing is charged by calling this' hints at a non-purchasing role, but there is no explicit 'use this to quote before buying' or 'use buy_report to actually purchase' guidance. The bundle special case is explained, but 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.