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

Annotations only carry the generic write/destructive/idempotency flags; the description adds real behavioral context the agent would otherwise lack: the COMMENT-level access requirement, the `tasks:write` API-key scope, and the per-user uniqueness cap that determines whether a repeat call succeeds or fails. It never says what a successful response contains, but the mutation prerequisites are covered.

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?

Four short sentences, front-loaded with the action, then parameter meaning, then the business rule, then auth requirements. Nothing is repeated from the schema or annotations.

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?

With no output schema, the description could say what a successful call returns (e.g. the created reaction), but for a small single-purpose mutation tool it covers action, parameter format, uniqueness constraint, and auth. The remaining gap is minor.

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%, so the baseline is 3. The description earns a bump by defining reactionType's format and adding the 'one reaction of each type per comment' constraint, which is a semantic rule about the parameter that the schema does not express.

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?

States a specific verb and resource ('Add an emoji reaction to a task comment') and immediately disambiguates the ambiguous parameter ('reactionType is the emoji code'). It is clearly distinguishable from pm_remove_comment_reaction and pm_list_comment_reactions despite similar naming.

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?

Usage context is implied by the access and scope requirements, and the one-reaction-per-type rule signals what happens on repeat calls, but there is no explicit routing to siblings such as pm_remove_comment_reaction for undoing a reaction or pm_list_comment_reactions for checking what already exists.

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