Set the account-wide default reaction

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

Annotations provide idempotentHint and openWorldHint, giving some behavioral context. The description adds that the emoji appears on long-press, which is a useful behavioral effect. However, it doesn't disclose side effects like overriding previous defaults or permission requirements, but the annotations lower the bar.

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 a single, front-loaded sentence with no filler. It efficiently conveys the core action in a clear, concise manner.

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?

The tool has three parameters and no output schema, yet the description provides minimal context. It doesn't explain the relationship between emoji and customEmojiId, nor the role of accountId, leaving an agent under-informed for correct invocation. The lack of return value info is also a gap.

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 for parameters is 0%, and the description provides no explanation for emoji, accountId, or customEmojiId. The term 'emoji' is implied by the description, but the other two parameters remain ambiguous. The description fails to compensate for the low schema 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?

The description clearly states the tool sets the quick reaction emoji for long-press, which is a specific action. It distinguishes from send_reaction by targeting the account-wide default rather than a specific message. However, the 'account-wide' scope appears only in the title, not the description.

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?

No guidance is provided on when to use this tool versus reaction-related siblings like send_reaction or get_default_tag_reactions. The description simply defines the action, leaving usage entirely implied with no exclusions or context.

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