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

Beyond the readOnly/idempotent hints, the description discloses key behavioral traits: weekly re-measurement with stable figures between releases, that it returns no brand names, the frozen public panel, and no auth/rate limits. These add significant context not available from annotations alone, with no contradictions.

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 structured with clear paragraphs: purpose, usage, output type, and data licensing/update cadence. It is somewhat longer than strictly necessary, but every sentence contributes meaningful information. The front-loaded purpose and usage guidance improve navigability.

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?

The description is highly complete given the tool's complexity and empty schema. It covers what the tool does, when to call it, how to interpret the results, the update frequency, licensing, and attribution requirements. The presence of an output schema reduces the need to detail return values, and this description fully addresses the operational context.

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?

The tool has zero parameters, so there are no parameter semantics to clarify. The description compensates by explaining what the response contains (rules, not figures), which aligns with the schema's empty properties. A baseline of 4 is appropriate for a no-parameter tool with thorough output description.

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 explicitly states the tool's function: 'The rules behind every figure this server returns,' and differentiates it from sibling tools by clarifying it 'returns rules, not figures' while naming get_visibility_index, get_brand_visibility, and get_history for figures and series. This is a specific verb+resource with clear scope and sibling distinction.

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 gives explicit when-to-use instructions: 'Call this before quoting a number as evidence, before comparing two releases, or whenever a user asks how the measurement was made or who publishes it.' It also names alternative tools for figures and series, providing clear usage boundaries.

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