Add reactions

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

Annotations indicate readOnlyHint=false and destructiveHint=false, so the agent knows it's a write but non-destructive operation. The description adds that it accepts unicode or custom emoji by name and supports multiple emojis. However, it doesn't disclose potential side effects, required permissions, or behavior for duplicate reactions, so it only partially exceeds annotation coverage.

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 a single, well-structured sentence that immediately states the action and key detail (single call). No wasted words; it is concise and 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?

For a relatively simple tool with annotations and a 75% schema coverage, the description provides enough context to understand the tool's core behavior. It misses minor details like rate limits or permission requirements, but these are not essential for basic usage and are partly covered by annotations. Overall, it is sufficiently complete for a tool of this 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?

The description adds some value by clarifying that emojis can be unicode or custom names, but the schema already covers emojis ('like a pasted emoji or a custom emoji name'). With 75% schema description coverage, the description does not significantly enhance understanding of the guild, channel, or message_id parameters beyond the schema.

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 function: 'Add one or more reactions to a message in a single call.' It specifies the action (add), the target (message), and the batch capability, distinguishing it from sibling tools like remove_reaction, clear_reactions, and get_reactions.

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 implies when to use this tool (adding reactions) and adds the batching guidance 'in a single call.' It doesn't explicitly mention alternatives or when not to use it, but the context and sibling tool names make the use case clear.

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