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

With no annotations provided, the description carries the transparency burden. It adds useful operational details about attachments (base64 encoding, passing them in the attachments array) and an explicit agent instruction to never claim attachments are unsupported. However, it does not disclose other behaviors such as authentication requirements, response format, or error handling.

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 compact: three sentences that are action-oriented and each provide meaningful guidance. It front-loads the core action and avoids filler, making it easy for an agent to parse quickly.

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 the tool has 5 parameters, no annotations, no output schema, and many sibling email tools, the description is incomplete. While attachment handling is well-covered, the 'instruction' parameter remains unexplained and no differentiation from send_outlook_email is provided, leaving agents potentially underinformed.

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 low (20%), affecting only the attachments property. The description adds value for attachments by specifying how to encode and pass files, but it leaves the 'to', 'subject', 'body', and especially the 'instruction' parameter without explanation. This partially compensates for the schema gap but not enough.

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 says 'Send an email via Gmail,' using a specific verb and resource. It also notes attachment support, which distinguishes it from sibling email tools like send_outlook_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?

There is no explicit guidance on when to use this tool versus alternatives like send_outlook_email or email_action. The description implies usage for Gmail email sending but does not discuss prerequisites, exclusions, or alternative selection.

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