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

Annotations already declare read-only, idempotent, non-destructive, which the description correctly does not repeat. Instead it adds real behavioral context: free-plan caps of 2 images and 12 results, information not available anywhere in the schema. It doesn't explain what the matches contain (similarity scores? screen metadata?) or pagination/result 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?

Two tight sentences, front-loaded with the purpose, followed by the workflow hint and the plan constraint. No filler; every clause adds actionable information.

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?

No output schema exists, and the description never characterizes what comes back beyond 'matches', leaving the agent to discover result shape on the first call. The plan limits and base64 format are covered, but the interaction between the `limit` parameter and the free-plan ceiling is unexplained.

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 0%, so the description carries the burden. It does clarify the critical format for `images` (base64, e.g. a UI screenshot), but the `limit` parameter is never mentioned — its relationship to the stated free-plan cap of 12 results vs. the schema default of 24 and max of 120 is left ambiguous.

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: find catalog screens that visually resemble supplied images. The 'by image' qualifier implicitly separates it from text-based search_screens, but it never names that sibling or similar_screens, so the agent must infer the 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?

Gives clear usage context and an explicit follow-up step ('then call get_screen on the matches to compare'), which is genuinely useful chaining guidance. It lacks any when-not guidance, e.g. when to prefer search_screens or similar_screens instead.

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