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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds one genuine behavioral fact beyond that: the result includes an explanation of why each flag is on or off, not just a boolean. It says nothing about empty/unknown flag keys or the scope of evaluation (all flags vs. a subset).

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 front-loaded sentence with no filler; the verb and scope come first and the return-behavior hint comes last. It is efficient, though arguably terse enough that a second clause on keys would have earned its place.

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 two parameters, no output schema, and no nested structures, the description handles the basic contract (evaluate flags for one user, return reasons) but omits the undocumented 'keys' parameter and the return shape beyond the vague 'explain why.' Adequate minimum viable coverage, not complete.

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 only 50%: user_id is documented in the schema, but the 'keys' array parameter is undocumented in both places. The description never mentions 'keys' or clarifies what omitting it does (evaluate all flags?), which is exactly the semantic gap the schema leaves open.

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 uses a specific verb and resource ('Evaluate feature flags for one user') and adds the scope qualifier 'for one user,' which separates it from the bulk definition-oriented sibling list_flags and from the mutation tool set_flag. It stops short of explicitly naming those siblings, so it lands at clear-but-not-differentiating-by-name.

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?

'For one user' implies the usage context (single-user evaluation vs. flag administration), but there is no explicit when-to-use, when-not-to-use, or named alternative. The agent must infer that list_flags is for definitions and this tool is for evaluation.

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