reactions_list

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is established. The description adds a useful limitation (only one emoji at a time; use messages_get for all) and return shape, but does not discuss pagination iteration, ordering, rate limits, or other runtime behavior.

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?

The description is well-organized with focused sections for purpose, usage, exclusions, example, and return value. It is not bloated, though the 'Returns' section partially duplicates what an output schema would provide.

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?

Given the rich schema, complete annotations, and clear usage guidance, the description covers nearly all necessary context. It could be slightly improved by explicitly stating that results are paginated and that 'after' should be used to fetch subsequent pages, but the schema already documents the cursor.

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?

All six parameters already have full descriptions in the schema (100% coverage), so the baseline is 3. The description's example and inline emoji mention add no semantic meaning beyond the schema, which already documents after, limit, type, channel_id, message_id, and emoji constraints.

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 opening 'Purpose' line names an explicit verb ('List'), a resource ('users who reacted'), and a scope ('with a specific emoji'), clearly distinguishing it from sibling tools like messages_get that return all emojis. It also reinforces the one-emoji scope in the 'When NOT to use' section.

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?

The description includes a dedicated 'When to use' section with concrete use cases ('Inspect poll results; identify upvoters') and a 'When NOT to use' section that explicitly names messages_get as the alternative when all emojis are needed. This gives the agent clear decision criteria.

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