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

With readOnlyHint and idempotent annotations already covering safety, the description adds genuinely useful behavior: under_review apps yield no tier or position for that category, and positions are never compared across categories. These are partial-result semantics an agent could not infer from annotations alone, though return formatting and error behavior are still not described.

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 focused sentences: the first front-loads what is returned and the scope, the second covers the under_review edge case, and the third states the cross-category constraint. Nothing is redundant or padded.

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 read-only comparison tool with no output schema and rich annotations, the description covers the key return fields, the omitted-list default, and two important behavioral caveats. It does not address what happens when a given app is absent from an explicitly requested category, nor does it mention the ten-app maximum, which are minor gaps.

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 50%, with the list parameter already described as a category slug whose omission means shared categories. The description reinforces the 'two or more apps' minimum and the shared-category default, but adds no new meaning about the keys format or the max ten apps, so it only partially compensates for the coverage gap.

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 states a specific verb ('compare') and resource ('apps'), and enumerates the returned dimensions (tier, position, score, components), so the operation is unmistakable. It does not explicitly differentiate itself from siblings like explain_ranking or get_app, which keeps it 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?

Usage is implied by 'Side-by-side ... for two or more apps' and by the omitted-list default, and the under_review caveat adds practical context. However, there is no explicit guidance on when to use this tool instead of calling get_app multiple times or explain_ranking, and no stated exclusions or alternatives.

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