Find pet by ID.

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

The description adds no behavioral context beyond the annotations. Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the agent knows it is a safe read. But the description does not disclose potential 404 behavior, response shape, or any other runtime details that would be useful for an agent.

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 one short, front-loaded sentence with no wasted words. It conveys the core action, though it could have been slightly more informative without becoming verbose.

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 simple read-only getter with minimal parameters and good annotations, the description is adequate but lacks details about the return object structure or error handling. Since there is no output schema, a bit more context would improve completeness, but the simplicity of the operation keeps it at a borderline acceptable level.

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 has 100% coverage for the sole parameter petId with a clear description 'ID of pet to return'. The tool description adds no additional parameter semantics, so the baseline of 3 is appropriate.

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 'Returns a single pet' clearly states the verb and resource, and the word 'single' helps distinguish it from sibling tools that return lists (e.g., find_pets_by_tags). However, it does not explicitly mention 'by ID' in the description itself, relying on the tool name and schema for that specificity.

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?

There is no guidance on when to use this tool versus alternatives. The description does not mention exclusions, prerequisites, or situations where another tool (e.g., find_pets_by_status) would be more appropriate. This is a bare statement with zero usage context.

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