Manage message reactions

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

Beyond the annotations (destructiveHint=true, readOnlyHint=false), the description discloses specific error outcomes (ALREADY_EXISTS, PERMISSION_DENIED), the requirement to use the authenticated user's own reactions for removal, scope prerequisites, and the raw_request path for custom emoji.

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 dense but every sentence carries operational or behavioral information. It is front-loaded with the core purpose and then efficiently covers actions, errors, custom emoji, and scopes without 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?

For a three-action tool with no output schema, the description is remarkably complete: it explains return contents for list, error conditions, permission boundaries, page_size/page_token usage, and scope requirements. Nothing critical is left for the agent to guess.

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?

Although schema coverage is 100%, the description adds important semantic detail: emoji must be the literal unicode character rather than a shortcode, reaction_name comes from list output, page_token enables pagination, and action determines which parameters apply. This meaningfully exceeds the bare 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 states a specific resource ('Emoji reactions on a message') and enumerates three distinct actions (add/list/remove), so an agent immediately understands what the tool does. It stands apart from sibling message and space tools because it is the only one operating on 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 gives clear per-action usage context, including filtering for list, deleting only via reaction_name, and the authenticated-user restriction. It also explicitly routes custom workspace emoji to raw_request, which is a useful alternative; however, it does not provide broad when-to-use vs. sibling-tool guidance.

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