Send Email

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

With no annotations, the description must disclose behavioral traits. It mentions the account tier requirement and threading behavior, but does not address mutation side effects (e.g., sent folder, quotas) or error conditions. This is partial disclosure, not comprehensive.

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 two sentences, front-loaded with the main purpose. It is concise and avoids extraneous details, though a bulleted list could improve scanability for longer descriptions.

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?

Given 7 parameters and no output schema, the description covers the core action, a prerequisite, and a key parameter nuance. However, it does not explain return values (e.g., sent email ID) or error scenarios, leaving some gaps for an AI agent.

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 baseline is 3. The description adds minimal extra meaning beyond the schema: it reinforces that in_reply_to enables threading (already in schema) and notes body_html as optional (already implied by not being required). No significant new semantics.

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 action ('Send an email from an inbox') with a specific verb and resource. It also adds nuance by mentioning replying within a thread via in_reply_to. However, it does not explicitly differentiate from sibling tools like check_inbox or search_emails, which limits distinction.

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 a prerequisite ('Requires a verified account (Tier 1+)') and explains a specific use case ('To reply within a thread...'). However, it lacks guidance on when not to use this tool or what alternatives exist among sibling tools.

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