slack_reactions_add

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

Annotations declare readOnlyHint=false and openWorldHint=true, so the agent knows this mutates external state. The description adds nothing beyond that: no required scopes, no idempotency behavior for duplicate reactions, no confirmation of whether the message must already exist.

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?

A single tight sentence with the action front-loaded and zero filler. It is efficient, though it is arguably under-specified rather than maximally concise.

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?

Parameters are fully covered by the schema and there is no output schema to explain, but for a mutation tool with only two annotations the description leaves out notable operational detail such as permission requirements and duplicate-reaction behavior.

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 description coverage is 100% and each parameter (name, channel, timestamp) is already documented in the schema with examples such as skin-tone modifiers. The description adds no parameter meaning beyond the schema, so the baseline 3 applies.

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 ('Add') plus resource ('emoji reaction') and target ('Slack message'), which is unambiguous. It does not differentiate itself from the neighboring slack_chat_post_message or explain how it relates to slack_conversations_history, but the core action is clear.

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?

There is no guidance on when to use this tool versus alternatives, no prerequisites (e.g. the bot must be in the channel), and no mention of what happens when the same reaction is added twice. Usage is implied by the name only.

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