detect_price_change

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

Annotations declare readOnly, idempotent, and non-destructive, so the baseline is covered. The description adds valuable context: cache-only (no API call), supported plans, and data availability timing. This goes beyond annotations, though it doesn't specify edge-case behavior like invalid or non-trading dates.

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 well-structured and front-loaded with the core purpose. However, there is minor redundancy between 'All plans.' and the later '[Supported plans]' list. Otherwise each section serves a purpose, and the length is appropriate.

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 simple one-parameter tool with an output schema, the description covers purpose, scope, usage, alternatives, availability timing, cache behavior, and parameter format. It is complete enough for an agent to select and invoke correctly without needing additional documentation.

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 provides only type and title for the date parameter, with 0% description coverage. The description compensates by specifying accepted formats (YYYY-MM-DD or YYYYMMDD), which is essential. It doesn't add more context (like trading-day restrictions), but for a single parameter this is sufficient.

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 first sentence clearly states the tool returns the daily advance/decline summary for all listed equities, using a specific verb and resource. It also distinguishes from siblings by naming get_advance_decline_ratio and get_sector_performance for related but different queries.

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 states when to use this tool ('Use for 値上がり銘柄数・値下がり銘柄数・騰落集計 queries') and provides alternatives for other use cases. Also includes a practical timing detail (data available ~17:15 JST on trading days), giving the agent clear selection criteria.

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