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

With no annotations, the description carries the transparency burden. It discloses that data are static, pins the census year to 2020, names the JMA source, and routes live queries to here. It does not discuss auth or rate limits, but for a read-only fact lookup this is reasonable.

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 dense, well-ordered sentence: purpose, parameter standard, returned fields, then sibling routing. No wasted words and the most important information is front-loaded.

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 single-parameter lookup with no output schema, the description lists the expected return fields and the alternative for live data. It leaves the exact representation of the centre point implicit, but an agent still has enough to select and call the tool correctly.

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 100%, so the schema already documents the code parameter fully. The description adds the JIS X 0402 standard in passing, but this is marginal beyond the schema's own '5-digit municipality code' example.

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 opens with a precise resource statement: 'Static facts for a municipality of Japan by 5-digit code' and then enumerates the exact returned facts. It also differentiates from the sibling here by explicitly telling the agent to use here for live values.

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 says 'Use the here tool with the centre point for live values,' which tells the agent when to prefer a sibling tool. The word 'Static' in the first sentence establishes the matching use case for place, so the when/when-not guidance is clear.

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