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

Annotations already mark the tool as readOnly, idempotent, and non-destructive. The description adds critical behavioral context: it returns live backend FoV when configured, cannot derive data from the model, and warns against inventing polynomial coefficients. This goes well beyond the annotations and fully informs the agent of the tool's behavior.

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 somewhat lengthy but front-loads the core purpose and contains no filler sentences. Every sentence earns its place by adding unique guidance or constraints. Could be trimmed slightly but remains effective.

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?

Given the absence of an output schema, the description thoroughly lists return fields (FoV, distortion, image-circle coverage, live stock, MTF/CRA/BFL) and explains limitations. It also clarifies what the tool cannot do, making it complete for the agent to understand what to expect.

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 input schema has 100% coverage with descriptions for all three parameters (sku, lensSku, lens_sku). The description does not add meaning beyond repeating the SKU examples (CIL250), which are already in the schema. Baseline 3 is appropriate since schema carries the burden.

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 clearly states it returns the Commonlands distortion model/status for one lens SKU, lists specific data returned (FoV, distortion, MTF, etc.), and differentiates from siblings by telling the agent not to use naive fallback methods. This exceeds the minimum viable detail.

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 explicitly lists when to use the tool (e.g., for FOV, distortion, MTF queries) and when not to use it (e.g., don't invent coefficients or use rectilinear fallback). While it doesn't name sibling tools directly, the 'do not use' instructions serve as clear guidance, making it a strong 4.

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