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

Annotations only provide the generic readOnlyHint=false / destructiveHint=false profile; the description adds genuinely new behavior — the bearer-token scope requirement ('scope: post'), the one-emoji-at-a-time rule, and the 3-distinct-emoji ceiling. The removal toggle clarifies that on=false is an undo-style operation, consistent with the non-destructive annotation rather than contradicting it. Return value and error behavior are still unstated.

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?

Three terse clauses in a single line: action, constraint, toggle, auth requirement. Every clause carries information an agent needs, and the primary action is placed first with the conditional auth note bracketed at the end.

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 4-parameter mutation with no output schema, the description covers action, limits, inverse operation, and auth scope — enough to invoke it correctly. It does not say what is returned on success or what happens when the 3-emoji limit is exceeded, a minor gap given the missing output schema.

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, but the description adds real meaning beyond the schema: 'up to 3 different per post' is a constraint absent from any parameter description, and 'on=false removes it' explains the boolean's effect better than the schema's bare 'default true'. The emoji/channel/post_id params are left to the schema, which is acceptable given full coverage.

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 ('react to a post') that is unique among the siblings — no other tool uses the verb 'react', so there is no ambiguity with post, delete_post, or vote. It also front-loads the domain constraint (one emoji, max 3 distinct per post) that defines the operation's limits.

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 supplies the key operational condition: 'on=false removes it', telling the agent how to accomplish the removal case with the same tool rather than looking for a separate unreact tool. It does not name alternatives or state when not to use this tool (e.g., vs. vote or mark_helpful), which keeps it below a 5.

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