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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered structurally. The description adds the efficiency rationale ("in one call") and the compared fields, but says nothing about return shape or behavior on invalid/missing ids. With annotations carrying the safety burden, a 3 is appropriate.

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 sentences with zero waste: capability and cardinality first, then the routing preference. Nothing to trim.

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 single-param, richly annotated read tool, the description covers what is compared and when to use it. The one residual gap is the exact response structure (per-id result objects vs. a table), which no output schema documents. Minor but real for a comparative tool.

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?

Only one parameter with 100% schema coverage; the schema already documents the 2–5 cardinality via minItems/maxItems. The description restates the count bound and identifies the values as "extension or app ids," adding no format or syntax detail beyond the schema. Baseline 3 is correct.

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 ("Compare") with a bounded resource set (2 to 5 extensions or apps) and enumerates the comparison dimensions: install count, rating, version, freshness. This is clearly distinguishable from siblings like get_extension or get_ranking.

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 names the alternative pattern ("repeated get_extension calls") and the condition that selects this tool ("when the question is comparative"). An agent can route correctly without opening either schema.

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