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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds behavioral context by specifying exactly what metadata is returned (title, description, total photos, cover photo, top contributors), which is valuable beyond the annotations. This goes beyond a simple scoping constraint and clarifies the nature of the operation.

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 a single, front-loaded sentence that covers the action, the resource, the input format, and the output contents. No superfluous words or repetition of schema/annotations. Every phrase earns its place.

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 tool with one parameter, clear annotations, and an output schema, the description is sufficient. It states what the tool does, how to address the topic, and what will be returned. No additional behavioral or return-format details are necessary because the output schema is present.

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 input schema only defines a string parameter with an example. The description compensates for the 0% schema coverage by explicitly stating the parameter is 'id or slug' and giving an example ('animals'), which fully explains the expected value format and meaning. This is exactly the kind of clarification the description should provide.

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 the verb ('Fetch') and the specific resource ('metadata for a single Unsplash topic'), with input via 'id or slug'. It distinguishes itself from siblings like 'topics' (plural list) and 'topic_photos' by focusing on the topic's metadata rather than the topics list or photos.

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 when to use this tool: when you need metadata for one specific topic, identified by id or slug. It doesn't explicitly name alternatives or state when not to use it, but the 'single' keyword and the inclusion of metadata fields provide clear context for its intended use, without exclusions.

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