React to a message

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

Annotations (readOnlyHint=false, openWorldHint=true) already signal a mutating, network-facing operation. The description adds one genuine behavioral fact beyond that: how to clear a reaction. It does not disclose whether a new reaction replaces an existing one (Telegram allows only one per user per message), nor any permission or failure behavior.

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, front-loaded with the core action and followed by the edge-case instruction. Every clause carries information and there is no filler.

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 need not explain return values, and the annotations cover the safety profile. However, for a mutating tool the description omits replace-vs-accumulate semantics, permission requirements, and chat identifier format, leaving real gaps for a 3-parameter 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 0%, so the description must carry the parameter burden. It usefully documents the clearing semantics of the emoji parameter, but says nothing about the accepted format of 'chat' (id vs username) or 'messageId', leaving two of three parameters undocumented anywhere.

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 (send) and resource (reaction/emoji) bound to a specific message, which is clearly distinct from the send_message, edit_message and forward_messages siblings. It does not explicitly contrast itself with any sibling, so it falls just short of the top band.

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 gives a conditional instruction for clearing reactions ('none' or ''), which is useful usage guidance, but offers no when-to-use vs when-not-to-use context or prerequisites (e.g. required permissions, whether the chat must be joined). Usage is only implied by the tool name and purpose.

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