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

Annotations already cover read-only, idempotent, and open-world behavior, lowering the bar. The description adds meaningful behavioral depth: pagination limit of 200 per page, the region result shape, and the 'no hits means no such region' semantics for query. This goes beyond what annotations alone convey.

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 yet information-dense, with no filler. It front-loads the operation and result shape, then gives usage guidance and parameter behavior in just a few sentences.

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 read-only lookup with no output schema, the description fully covers what is returned, pagination, query semantics, and when to prefer an alternative. An agent has enough context to call it correctly without further investigation.

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?

Input schema coverage is 100%, so the baseline is 3. The description adds slight interpretive value for query ('no hits means the map really has no such region') but mostly restates what the schema already documents about mapId, query, offset, and 200-region pages.

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 names a specific verb and resource ('Look up one map'), enumerates the returned data fields, and clearly distinguishes this tool from render_map and list_maps. An agent can tell exactly what it will get and which sibling it should use instead.

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?

It explicitly says this tool is rarely needed before renderingainer and points to render_map as the alternative that accepts aliases and corrects typos. It then lists concrete use cases: building a full dataset, inspecting region naming, or resolving unmatched keys.

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