react

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

Annotations already indicate destructiveHint=true, confirming mutations. The description adds that the tool can add or remove reactions, which aligns with the annotation. However, it does not disclose additional behavioral traits like permission requirements, rate limits, or side effects (e.g., notifications). Minimal added value beyond annotations.

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 consists of two concise sentences, each serving a clear purpose: the first announces the core functionality, and the second provides simple usage instructions. No unnecessary words or repetition.

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 an output schema present, the description does not need to explain return values. It covers the main action and basic parameter usage. A minor gap: the default value of the 'operation' parameter (add) is not mentioned, but the schema provides it. Overall, sufficiently complete for a tool with good annotation coverage.

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 description coverage is 100%, so the schema already documents all parameters. The description briefly mentions using targetType and targetId but does not add new semantic meaning beyond what the schema provides. Baseline score of 3 is appropriate.

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 clearly states the tool's action ('Add or remove an emoji reaction') and specifies the target resources (thread, comment, or conversation message). The verb and resource are specific, and it is easily distinguishable from sibling tools like 'reply' or 'delete-object'.

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 provides basic usage guidance (how to specify targetType and targetId) but does not explicitly state when to use this tool versus alternatives or mention any prerequisites. Usage is implied but lacks exclusionary guidance.

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