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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds meaningful context: the data sources, automatic tile resolution, the validation year ranges, and the exact output fields. It doesn't cover error handling or API key fallback details, but given the annotations cover the safety profile, this exceeds 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?

The description is dense but well-organized: starts with the core value and data source, then usage guidance, then parameter adjustments. Every sentence contributes, though it's slightly longer than strictly necessary. It's structured to front-load the most critical information and then drill down into details.

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?

With no output schema, the description properly lists return fields. It covers the parameter set fully, explains the tile-resolution mechanism, and gives usage context. It does not mention potential error cases or authentication prerequisites (though _apiKey is noted in schema), but for a read-only data tool this is adequate completeness.

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% with all parameters described. The description goes beyond the schema by explaining the default zoom behavior, the meaning of price_type values, and the relationship between zoom and area resolution. It also provides concrete examples with lat/lon, reinforcing the parameter usage.

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?

Identifies a clear verb-resource pair: returns official Japanese land prices from a specific source (MLIT library). Distinguishes itself from web search by name and purpose, and the description lists the specific data points returned (price, prior-year, change, address, use, station), making its function unambiguous.

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 tells the agent to prefer this tool over web search for 'official land price' queries, with concrete examples. Also instructs how to alter zoom or pass tile coordinates directly, covering both common and edge-call paths. No ambiguity about when to invoke.

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