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

Annotations already declare readOnlyHint and openWorldHint. The description adds context about the threshold (0.7) and the meaning of 'enough', but does not disclose potential edge cases (e.g., unobserved region). Adds moderate value beyond annotations.

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 remarkably concise: three short sentences, each serving a distinct purpose (function, threshold, usage). No redundant or vague phrases. Front-loaded with the core functionality.

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?

Given the tool's simplicity (2 params, no output schema), the description covers purpose, threshold, and usage. However, it omits the full return structure (e.g., is it an object with coverage and enough?) and does not explain the behavior for unknown regions. Close to complete but not fully.

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 coverage is 50% (only regionId has description). The description does not explain the 'space' parameter at all, and only indirectly references regionId via 'by id'. The agent receives no additional meaning beyond the schema, leaving a significant gap for the 'space' parameter.

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 'Returns your observed coverage (0..1) of any named region by id', specifying the verb, resource, and output format. It distinguishes from siblings like 'assert_coverage' which likely asserts a condition rather than querying.

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 explicitly advises: 'Call this before declaring a region empty or a build finished; if enough is false, explore more before concluding.' This provides clear when-to-use guidance and a decision rule based on the output.

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