send_mail

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

Annotations already indicate readOnlyHint=false and idempotentHint=false, so the side-effecting nature is covered. The description adds useful behavioral context beyond that: the email is sent via the account-specific SMTP server and the tool returns a confirmation message on success. It does not explicitly warn that sending is irreversible, but this is not a contradiction and the non-idempotent annotation already signals it.

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 well-structured: a one-sentence purpose statement, a clarifying mechanism sentence, a compact Args list that matches every parameter, and a Returns line. Every sentence contributes necessary information, and the content is front-loaded with the core purpose.

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 side-effecting tool with seven parameters and no schema-level descriptions, the description is complete enough for an agent to invoke it correctly. It covers all arguments, prerequisite account discovery, optional fields, default behavior, and the success return. An output schema exists, so the absence of detailed return-shape documentation is acceptable.

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 0%, so the description carries the full burden for all seven parameters. It explains account_id discovery, the required list of recipients, subject/body roles, CC/BCC as optional lists, and the is_html plain-text/HTML switch with its default. This is meaningful semantic guidance that the schema alone does not provide.

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 opens with a specific verb and resource: 'Send an email through a Nextcloud Mail account.' It further clarifies the mechanism ('via the SMTP server configured for the account'), which distinguishes it from siblings like send_message and mail-manipulation tools. The name and description align without tautology.

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 gives clear workflow guidance by telling agents to use list_mail_accounts to find the account_id. It also makes the required recipient condition explicit ('at least one required'). It does not explicitly state when not to use this tool versus send_message, but the Nextcloud Mail framing provides enough context to select it correctly.

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