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

Annotations already provide readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds deterministic and no LLM, indicating consistent, non-AI results, plus a rate limit and free cost. This enriches the behavioral profile beyond the annotations without contradiction.

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?

A single, front-loaded sentence conveys purpose, differentiation, and key constraints, followed by a rate limit. Every word earns its place; no filler or redundancy.

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 two-parameter tool with no output schema, the description adequately conveys what the tool checks and its deterministic nature. It does not specify the exact output format, but the agent can reasonably infer a boolean or status result. Rate limit is also mentioned. Slightly missing output details, but not critical for a precheck.

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% with clear descriptions for image_url and image_base64. The tool description does not add any parameter-level meaning beyond what the schema already states, so the baseline of 3 applies.

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: a free precheck that determines face detectability and photo quality (clipping/color cast) before paid portrait_analysis. Explicitly distinguishes itself from the sibling portrait_analysis by framing itself as a prerequisite.

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?

Tells the agent exactly when to use it: before paying for portrait_analysis, to avoid wasting money on an unanalyzable image. Also gives a concrete rate limit (10/hour/IP), which is a usage constraint. No ambiguity about its role.

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