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

Annotations already declare readOnlyHint, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuine behavioral context beyond that: the input accepts 2-5 items and the response contains stored details plus a diff of differing fields, which tells the agent what it will get back from a comparison.

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, no filler, and the input constraint plus the return content are both front-loaded. Every clause carries information an agent would otherwise have to guess.

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?

A single fully-documented parameter, complete annotations, and an output schema mean the description need not explain return values, yet it still summarizes them. Minor gaps remain around error behavior for unknown or ambiguous identifiers, but nothing essential to calling the tool 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 coverage is 100% and the schema already documents the records array with minItems 2, maxItems 5, and an example. The description's 'by id, slug, or exact name' matches the schema text without adding format or matching semantics (e.g., case sensitivity, ambiguity handling), so 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?

States a specific verb (compare) and resource (directory items), plus the accepted 2-5 item range and the identifier forms. It does not name get_record or search_records as alternatives, so the differentiation from siblings is implied rather than explicit.

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 only implied: comparing multiple items is what the tool is for, and the 2-5 bound hints that a single-item lookup belongs elsewhere. No when-not guidance or named alternative is given, leaving the agent to infer the boundary with get_record.

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