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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, covering the safety profile. The description adds no additional behavioral context such as not-found behavior or response format, which is acceptable for a simple read operation but does not elevate beyond the baseline.

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?

'Single character by id' is exceptionally concise, using only seven words with no filler or redundancy. It is front-loaded, immediately conveying the core purpose.

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?

The tool is a simple single-parameter lookup with a full output schema and strong annotations. The minimal description is sufficient for an agent to understand the core function. It does not address not-found behavior or selection guidance versus 'characters', but these are not critical given the output schema and sibling context.

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 0%, so the description must compensate. It does mention 'by id', tying the sole parameter to its purpose, but adds no detail beyond the parameter name and type already present in the schema. For a single obvious 'id' parameter, this meets the minimum but does not enrich understanding.

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 'Single character by id' clearly indicates a lookup of a single entity by identifier, and the contrast with the sibling 'characters' (plural) helps distinguish it as a singular resource accessor. However, it lacks an explicit verb like 'get' or 'fetch', so it is not maximally explicit.

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?

No explicit when-to-use or alternative guidance is provided. The phrase 'by id' implies use when a specific character ID is known, and the sibling 'characters' suggests the plural alternative, but this is implicit rather than directly stated.

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