reply_to_email

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly indicates this is a mutation operation (reply action) and specifies constraints (requires existing email ID, cannot send new emails). However, it doesn't mention authentication needs, rate limits, error conditions, or what the response looks like, leaving gaps for a mutation tool.

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 perfectly concise with three sentences that each earn their place: states the purpose, provides critical constraint, and gives alternative guidance. It's front-loaded with the core functionality and wastes no words.

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 tool with no annotations and no output schema, the description provides good purpose and usage guidance but lacks behavioral details about permissions, response format, or error handling. The 100% schema coverage helps, but more context about the operation's behavior would be beneficial given the complexity.

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 100%, so the schema already documents all 6 parameters thoroughly. The description adds no additional parameter semantics beyond what's in the schema. The baseline score of 3 is appropriate when the schema does the heavy lifting for parameter documentation.

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 specific action ('Reply to an existing email') and resource ('email'), distinguishing it from sibling tools like create_campaign for sending new emails. It explicitly differentiates from alternatives by stating 'This can only be used to reply to existing emails, not to send new emails.'

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 provides explicit guidance on when to use this tool ('reply to existing emails') and when not to ('not to send new emails'), with a clear alternative named ('Use campaigns for sending new emails'). It also mentions prerequisites ('You must provide the ID of an existing email to reply to').

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