create_merge_request_note_emoji_reaction

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

Annotations only include openWorldHint: true, which indicates the tool may have side effects. The description goes beyond this by stating 'It changes remote GitLab state and requires the necessary project or group permission' and that GitLab returns errors for invalid requests. This adds useful context about side effects and error behavior, but it does not detail specific error types or rate limits, and the description does not contradict annotations, so a 3 is appropriate.

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 paragraph of about 3 sentences. It is focused and avoids fluff. The key purpose is front-loaded. However, it packs a lot of information into a long first sentence that could be broken up for readability, so it's a 4 rather than a 5.

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 covers the core purpose, usage context, permission requirements, and error behavior. It also mentions discussion_id handling and identifier formats. However, it lacks details on what the response looks like (though no output schema is provided) and how the tool behaves regarding idempotency or rate limits. Given the complexity of the GitLab API, a bit more detail would improve completeness, so it's a 3.

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 input schema has 100% coverage for all 5 parameters, so the schema already documents each parameter. The description adds some context about using discussion_id for thread replies and mentions using numeric IDs or URL-encoded paths for project_id, but these are already partially in the schema descriptions. Since coverage is high, baseline is 3, and the description provides minimal extra value beyond what the schema says.

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 'Add an emoji reaction to a merge request note', specifying the verb (add), resource (emoji reaction), and target (merge request note). It distinguishes from sibling tools by mentioning discussion_id for thread replies, but there are many closely related sibling tools (create_merge_request_emoji_reaction) that are not explicitly differentiated, so it loses a point.

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?

It provides explicit guidance on when to use this tool: 'Use this for a new resource or action; choose the corresponding update or edit tool when the resource already exists.' It also mentions the need for discussion_id for thread replies and correct identifiers. However, it does not explicitly name alternative sibling tools or list conditions for when not to use it, so it's a 4 not a 5.

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