create_reaction

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

No annotations are provided, so the description must carry the full burden of behavioral disclosure. It states the core action and that a confirmation string is returned, but it does not mention permissions, whether adding the same reaction twice fails, whether the reaction is created on behalf of the user identified by user_google_email, or any other side effects.

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 compact, well-structured with Args and Returns sections, and provides concrete examples without unnecessary prose. It loses a point because the Args section omits one of the three required parameters, making the structure slightly incomplete.

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 mutation-style tool with no annotations, zero schema-level parameter descriptions, and a required but undocumented user_google_email, the description is not complete enough. The output schema exists, so the return value is less of a concern, but usage context, parameter coverage, and behavioral details are all missing.

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 compensate. It provides useful examples for message_id and emoji_unicode, but the required user_google_email parameter is not described anywhere, leaving a significant semantic gap for an agent.

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 uses a specific verb and resource: 'Adds an emoji reaction to a Google Chat message.' This clearly distinguishes it from the many sibling tools, none of which cover Chat reactions, and gives an agent an immediate understanding of the operation.

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 intended usage is implied by the action: use this when a reaction needs to be added to a Chat message. However, there is no explicit guidance about when not to use it, no reference to obtaining a message_id via related tools like get_messages or search_messages, and no mention of prerequisites or alternatives.

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