send_reaction

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

With no annotations, the description carries the full burden and it does state the core mutation: a reaction is added to a message. It does not disclose side effects such as whether an existing reaction is replaced, whether the reaction is visible publicly, or what error behavior occurs, leaving some behavioral ambiguity.

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. Every word contributes to the core meaning, and the length is appropriate for a tool with three straightforward parameters.

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?

The definition is minimally viable for a simple react-to-message tool because the action and required parameters are clear from the description plus schema. However, the 0% schema description coverage, lack of sibling differentiation, and absence of any success/error or return-value note leave the agent to make assumptions about edge cases.

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 0%, so the description should compensate, but it does not explain any parameter semantics beyond the inferable roles of chat_id, message_id, and emoji. It gives no guidance on emoji format (Unicode vs. shortcode), how chat_id should be represented, or what makes a valid message_id.

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 ('React'), a clear resource ('a message'), and the payload type ('an emoji'). This makes it immediately distinct from sibling tools like send_message and forward_message, which send new content rather than attach a reaction.

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?

There is no explicit when-to-use guidance, no exclusions, and no mention of alternatives. However, the wording 'React to a message with an emoji' implies the appropriate use case when an agent needs to attach an emoji reaction rather than send or edit a message.

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