create_reaction

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

No annotations provided, so the description carries full burden. It discloses side effects ('creates a reaction visible to everyone'), limitations (Unicode only), and auth requirements. Could be more detailed about idempotency or response, but covers key behavioral aspects.

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?

The description is four sentences, each serving a purpose: action, side effects, limitations/alternative, auth. No redundant information, efficiently 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?

Given no annotations, the description covers purpose, usage guidelines, side effects, and limitations. An output schema exists, so return value details are not needed. The description is thorough enough for a typical create 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 coverage is 100%, but the description adds value by clarifying that 'emoji_unicode' must be a Unicode character and that custom emoji are not supported. This extra context helps the agent avoid invalid inputs.

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?

The description clearly states 'Add an emoji reaction to a Chat message' with a specific verb and resource. It distinguishes from sibling tools like 'send_message' by noting that it is for reactions, not posting new messages.

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 explicitly says when not to use it (Custom Workspace emoji not supported), provides an alternative ('For posting a new message use send_message'), and specifies the required OAuth scope ('Requires the chat_write OAuth scope').

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