forward_email

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

The description extensively discloses behaviors beyond annotations: the IMAP-read-first atomicity guarantee (call fails before any SMTP session opens), subject derivation without stacking a second 'Fwd:' prefix, plain-text re-composition with the caller's note placed above, MIME-type-preserving attachment re-attachment, per-recipient succeeded/failed/unknown delivery reporting with separate Sent-copy outcome, and no automatic retry of ambiguous effects. Annotations only declare non-read-only/non-idempotent; the description explains what that means in practice.

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 dense (~95 words) but every sentence covers a distinct behavioral facet: failure atomicity, subject/body/attachment composition, and delivery reporting. It is front-loaded with the core purpose and contains no filler, though its length demands careful reading.

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 an 8-parameter mutation tool, the description covers the critical operational concerns: when the call fails, how content is composed, attachment semantics, delivery-status reporting, and retry policy. Combined with 100% schema coverage, an output schema, and annotations, little is missing; only an explicit pointer to allowed-recipient checks or send_email routing would make it fully 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, but the description adds genuine value: it clarifies include_attachments re-attaches with original MIME types unless false, explains the body's placement above a re-composed plain-text block, and reveals the auto-derived subject prefix that affects the delivered message. Most parameter meaning still comes from the schema, hence not a 5.

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 opening sentence states a specific verb + resource + target: 'Forward an existing message to new recipients using the specified account.' This clearly differentiates it from siblings like send_email (composing a new message) and get_emails_content (reading), and the required email_id (source UID) makes the resource unambiguous.

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 implies the use case — forwarding requires an existing source message, so an agent must first obtain an email_id — but it never explicitly contrasts this with send_email for composing new messages or names alternative tools. The distinction is inferable from the first sentence but not stated as concrete guidance.

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