Add reaction

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

No annotations are provided, so the description carries the full burden. It adds useful behavioral context about accepted emoji formats (unicode or custom <:name:id>), which goes beyond the schema, but it does not disclose side effects, idempotency, permission requirements, or error behavior. It provides some value but not rich behavioral context.

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?

Two sentences, each earning its place: the first states the purpose, the second clarifies the emoji parameter format. No redundancy, no fluff, and the purpose is front-loaded.

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 description adequately covers what the tool does and the key parameter format, but with no annotations and no output schema, it omits important context such as return values, error cases, and whether repeated reactions are idempotent. For a simple tool, this is minimally viable but has clear gaps.

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 baseline is 3. The description meaningfully adds to the schema's generic 'The emoji to react with' by specifying the accepted formats (unicode emoji or custom emoji in <:name:id> format), which helps the agent select a valid emoji value.

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 states a specific verb and resource: 'Add an emoji reaction to a message.' This clearly distinguishes the tool from siblings like send_message and read_messages, making the purpose unambiguous.

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 usage context is implied by the specific purpose—use this when you want to react to an existing message—but there is no explicit guidance on when to use it versus alternatives, nor any exclusions mentioned. The description does not reference sibling tools like send_message or read_messages.

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