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

Annotations already cover read-only, idempotent, open-world semantics, and the description adds real substance on top: results are live, the difficulty score is a 0-100 heuristic derived from rating volume and name matches rather than Apple search volume, and the response includes a top-10 list of apps rated under 4.2. It does not mention rate limits or result-count limits for the live lookup.

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 dense paragraph that leads with the selection trigger, then the required inputs, then return contents and the difficulty caveat. Every sentence carries information, though the return-value enumeration is somewhat long given an output schema exists.

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 two-parameter read tool with full schema coverage, an output schema, and annotations covering the safety profile, the description supplies the trigger, the inputs, and a caveat about how to interpret the difficulty metric. Nothing an agent needs to invoke it correctly is missing.

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%, and both parameters (term, country) are already documented with format, pattern and the us default. The description's 'Pass term and country' adds no syntax or constraint detail beyond the schema, so the baseline 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?

Names a specific resource (live iPhone App Store search results for a term) and the exact user intent it serves, with a concrete example query. An agent can distinguish it from sibling tools like app_tracker_estimate or app_tracker_charts, which serve different questions, without opening any schema.

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 the triggering situation ('when the user asks who ranks for a search term or how crowded it is') and gives a sample phrasing. It stops short of naming which sibling to use instead when the user wants volume estimates or historical charts, so the routing guidance is good but not exhaustive.

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