react

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

Annotations already declare readOnlyHint=false, destructiveHint=false and idempotentHint=true, so safety is covered. The description adds genuinely useful behavior the annotations do not: the empty-emoji removal path and the fact that a new reaction replaces the previous one (single reaction per user).

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?

One compact sentence covering the react path plus a short second clause for the removal/replace semantics. Nothing is wasted and the primary action is front-loaded.

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?

An output schema exists so return values need no explanation, and annotations carry the safety profile for this mutation. It is nearly complete, but the three undocumented identifier parameters leave a small gap for a 4-parameter write tool.

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 only 25% — 'chat', 'message_id' and 'account' are undocumented in both schema and description, so there is a real gap. The description does explain the emoji parameter's empty-string semantics, which duplicates the schema entry, so it compensates only partially.

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 ('Réagit à un message') plus the removal variant, so the agent knows exactly what the tool does. It does not name or contrast with any sibling tool, which keeps it short of a 5.

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 implicitly tells when to use it ('empty emoji' for removal), which is the key branching condition. However it names no alternatives and gives no prerequisites, e.g. whether the message must be in your own chat or what account selection implies.

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