reply_to_email

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

Annotations already declare destructiveHint=true, and the description aligns by emphasizing 'immediately send.' It adds valuable context not in annotations: the correct threading behavior via In-Reply-To/References headers and the PROTONMAIL_ALLOW_SEND requirement. It doesn't explicitly warn about irreversibility, but the annotation covers the destructive nature.

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?

Four sentences total, front-loaded with the core action, then providing usage alternatives and a prerequisite. No filler or repetition of schema details.

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 high-complexity, destructive send tool with no output schema, the description covers core purpose, when to use vs alternatives, required permission, and threading behavior. It misses minor details like dryRun behavior, but these are sufficiently documented in the schema. The description is complete enough for an agent to select and invoke correctly.

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%, so the schema already documents all 14 parameters with descriptions. The description adds no parameter-specific semantics beyond referencing emailId and the general send action. It does mention the auth requirement, which is not tied to a parameter, so baseline 3 is appropriate.

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's function: 'Immediately send a reply to an existing email, threading it correctly via In-Reply-To and References headers.' It distinguishes itself from sibling tools by naming alternatives like create_reply_draft and reply_all_email.

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?

Explicit usage guidance is provided: 'Use when you have an emailId and want to send the reply right away.' It also gives when-not-to-use alternatives: 'Prefer create_reply_draft to save the reply for review first, or create_thread_reply_draft when replying from a threadId. Use reply_all_email to reply to all original recipients.'

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