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

Annotations already declare readOnly/idempotent/non-destructive; description adds data source and auth requirements ('Data: dashboard.e-stat.go.jp, no auth required') and clarifies that the tool returns metadata rather than indicator values. No contradiction with 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?

Three short segments: the operation, the use-case, and the data source. Every sentence carries unique information, front-loads the core behavior, and there is no filler.

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 2-param lookup tool with output schema and read-only annotations, the description is complete: it covers both input modes, names the return content (name, level, valid date range, catalog scope), references the dependent get_data tool, and states source/auth. Nothing needed for correct invocation is missing.

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 100% and already documents both params, including the omit-region_code behavior and examples ('13000' Tokyo, '00000' Japan). The tool description mirrors this but adds no new parameter-level meaning, so baseline 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?

States a specific verb and resource: 'Get metadata for one e-Stat Statistics Dashboard region code' and the alternative of fetching the full catalog. It distinguishes from sibling get_data by framing this as metadata lookup and explicitly references discovering region codes for estat-japan-dashboard.get_data.

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?

Explicitly instructs to use this to discover region codes for estat-japan-dashboard.get_data, and explains the two invocation modes (single code vs omit for full catalog). It doesn't explicitly contrast with sibling indicator_info, but the primary workflow is clearly specified.

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