send_reaction

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

Discloses reversible behavior via empty emoji, return value of 'Reaction sent', and hints that it is idempotent (aligns with annotation). No contradiction with 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?

Three concise sentences; first sentence immediately states core purpose. No superfluous content.

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?

For a 4-parameter tool with no output schema, the description covers all: purpose, usage guidance, return value, and parameter hints. Sibling tools are mentioned. Complete given the tool's complexity.

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 already describes all parameters thoroughly. Description adds no significant new semantics beyond restating the emoji empty string case.

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 verb 'Add or replace an emoji reaction on an existing message' and distinguishes it from siblings by specifying 'for a fresh message use send_message and for a quoted reply use send_reply'.

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?

Explicitly tells when to use (react to existing message) and when not (use send_message for fresh, send_reply for quoted reply), and explains reversibility with empty emoji.

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