create_merge_request_emoji_reaction

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

Annotations provide only openWorldHint=true, which is a minimal signal. The description compensates strongly by stating 'It changes remote GitLab state', requiring permissions, and listing possible error types (validation, conflict, permission, rate-limit). This discloses side effects and failure modes beyond what annotations convey. 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?

The description is longer than typical but every sentence adds value: purpose, usage, behavior, error handling, and parameter guidance. It is front-loaded with the core action and example. Slightly verbose in the final sentence about pagination, which isn't relevant to this tool, but overall it is well-structured and not redundant.

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?

Given the tool's simplicity (3 params, no output schema), the description covers all necessary aspects: purpose, usage distinctions, side effects, permissions, error behavior, and parameter format. An agent has everything needed to call this tool correctly without further inference. The mention of pagination is a minor irrelevant addition, but completeness is high.

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% (all 3 parameters have descriptions). The description adds context on how to supply project_id ('numeric ID or complete URL-encoded path') and emphasizes using required identifiers exactly as documented. While schema already covers parameter meaning, the description reinforces format nuances, providing marginal added value above baseline.

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 ('Add an emoji reaction') and resource ('merge request') with concrete examples ('thumbsup, rocket, eyes'). It clearly distinguishes from related tools by noting when to use update/edit tools instead, so an agent can differentiate it from siblings like create_merge_request_note_emoji_reaction or update_merge_request without needing to inspect schemas.

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 explicitly provides usage context: 'Use this for a new resource or action; choose the corresponding update or edit tool when the resource already exists.' It also mentions permission requirements and error behavior, giving clear guidance on when and how to invoke this tool versus alternatives. No ambiguity remains.

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