fetch

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. The description adds value beyond those by specifying error behavior for malformed ids and removed listings. The only minor redundancy is restating 'read-only' when annotations already provide it.

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, front-loaded with the core purpose, then delivers id format, behavior, errors, and exclusions in a logical order. Every sentence earns its place and none are wasted.

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 single-parameter tool with no output schema, the description is complete: it specifies the id format with examples, explains error cases, declares read-only behavior, and routes the agent away from the wrong sibling tool. Nothing essential is missing.

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 100%, so the baseline is 3. The description adds further value by providing concrete id format examples ('facebook:12345' or 'ebay:v1|123|456') and by clarifying that ids from search_marketplace are not valid here. This goes beyond the schema's brief description.

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 ('Fetch one listing in full') and immediately ties it to ids returned by the search tool. It also distinguishes itself from get_listing_details by explicitly saying what it is not for, so an agent can pick the correct tool 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?

The description clearly states when to use the tool: for ids returned by the search tool. It also gives an explicit exclusion and alternative: ids from search_marketplace should use get_listing_details instead. This is direct, actionable routing guidance.

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