slack_add_reaction

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

Annotations already declare readOnly=false, destructive=false, idempotent=false and openWorld=true, so the mutation and non-idempotency profile is covered structurally. The description adds only the word 'authorized', hinting that the emoji must exist/permitted in the workspace, but it does not say what happens on duplicate reactions or on invalid emoji — the two most likely failure modes for a non-idempotent write.

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?

Two short sentences, zero waste, with the core action front-loaded and the parameter hint trailing. Nothing to trim and nothing buried.

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 small 3-parameter mutation with no output schema, the description is minimal but workable: it names the action and the one undocumented parameter. It omits the duplicate-reaction behavior and the success response, which matter for a non-idempotent write with no output schema to fall back on.

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 67%: channel and timestamp are already documented in the schema, leaving only 'name' undocumented there. The description addresses exactly that gap by saying 'use an emoji name without colons', which is useful guidance (though the pattern already excludes ':'). It adds nothing about how to obtain the message timestamp or channel ID 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?

States a specific verb and resource: 'Add an authorized emoji reaction to a message.' An agent immediately knows the operation. No sibling tool touches reactions, so explicit differentiation from siblings is less critical, though it never says how it relates to the message-read/send tools.

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 statement of when to use this versus other tools, no prerequisites beyond the ambiguous word 'authorized', and no mention of what to do if the reaction already exists. The agent must infer usage entirely from the tool name and schema.

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