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

The annotations only declare it a safe, idempotent read; the description adds the non-obvious behavioral layer — advanced queries return full pages only on paid plans, free keys get truncated results, and pagination past page 1 requires a paid plan. These are exactly the constraints an agent cannot infer from schema or annotations.

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?

Three sentences, front-loaded with what the tool does before the plan caveats. The paid-plan constraint is stated twice (truncation for advanced queries and pagination lockout), which is a slight redundancy rather than waste.

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?

With 12 params, no required fields, no output schema, and sparse annotations, the description carries the burden well by covering tier gating and search-mode behavior. It doesn't describe result shape or per-platform differences (web store vs. app store result fields), which would be the remaining gap.

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 coverage is already 92%, so the baseline is 3; the description beats that by grouping the eight parameters that escalate to an advanced query (category, minUsers, maxUsers, minRating, minRatingCount, updatedWithinDays, author, sortBy) and noting default sort behavior implicitly. It omits platform, page semantics, and query matching scope, which the schema already covers.

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+resource (find browser extensions or mobile apps) and immediately names the two search modes (keyword-only vs. numeric filters). It doesn't differentiate itself from siblings like `search` or `search_source_code`, so it stops short of a 5.

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?

Explains when each mode is appropriate by tying it to plan capability: keyword-only works anywhere, filters/sortBy trigger an advanced query. It does not point to the sibling tools (get_extension, compare_extensions, search) for follow-up work, so no explicit alternative routing.

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