send_email

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

With no annotations, the description discloses immediate send, failure conditions, and return of delivery confirmation. However, it does not mention whether a copy is saved to sent folder or 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?

Four sentences, each adding unique value: purpose, usage context, alternatives, failure/return info. No redundant or vague statements.

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 tool with 9 parameters and no output schema, the description covers purpose, usage guidelines, failure modes, and return behavior. Could mention sent folder or attachment constraints but is fairly complete.

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 baseline is 3. The description adds context about Proton Bridge SMTP and failure conditions but does not elaborate on individual parameter usage beyond the schema.

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 'Compose and immediately send a new outbound email' (specific verb+resource) and distinguishes from sibling tools like create_draft and reply_to_email by specifying one-shot use case.

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?

Explicitly says to use for one-shot messages needing no review, and advises prefer create_draft for review or reply_to_email for replies. Also lists failure conditions (PROTONMAIL_ALLOW_SEND false, SMTP unreachable).

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