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

With no annotations, the description carries the full burden of behavioral disclosure, and it does so thoroughly. It states the operation is read-only, 'spends nothing', returns listings regardless of verification, and honestly reports payment_verified. It also explains what the reliability score means and what it does not mean, which is valuable beyond schema information.

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 purpose and remains information-dense. Most sentences add meaningful context about reliability, verification, and cost. The 'Method: URL' clause feels slightly extraneous and the reliability explanation is lengthy, but everything is relevant enough that it stays within reasonable bounds.

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?

Despite having no output schema, the description enumerates the returned fields, including the nested reliability object with its possible values and meaning. It covers edge cases like unverified listings and unscored reliability, and the parameter provenance ties cleanly to sibling tools. An agent has enough to call this correctly.

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 only one parameter and schema description coverage is 100%, so the schema already fully documents 'id' as 'Listing uuid or slug, as returned by search_apis or list_apis'. The description repeats this same meaning without adding new format, constraints, or examples, so the baseline of 3 applies.

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 opens with a specific verb and resource: 'Fetch a single live listing by its id or slug'. It differentiates from sibling tools by emphasizing 'single' retrieval versus listing/search, and even names the source of the id ('as returned by search_apis or list_apis').

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 clearly establishes this tool is for fetching one listing by id or slug, and it notes where those identifiers come from ('as returned by search_apis or list_apis'). It does not explicitly spell out when not to use it or contrast it with alternatives, but the single-vs-many distinction gives clear contextual guidance.

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