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

No annotations exist, so the description carries full behavioral burden. It discloses that actions trigger on matching emails and lists action types, but omits important behavior like rule evaluation order, priority handling, stop semantics, or side effects of actions (e.g., sending auto-replies). The schema includes priority and stop, but the description does not add context beyond the basic trigger condition.

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 a single, compact sentence that conveys the core purpose and enumerates the supported action types. No unnecessary words, and it is front-loaded with the primary action.

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?

Though the tool has nested objects and six parameters, the schema descriptions are comprehensive (100% coverage), so the description does not need to explain each parameter. It provides the core purpose and action types, which is sufficient for an agent to select this tool. No output schema exists, but for a creation operation the return value is not critical.

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% with thorough parameter descriptions, so baseline is 3. The description adds only a list of action types, which already appears in the schema enum. It provides no extra semantic meaning for parameters beyond what the schema already documents.

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 'Create a rule that triggers actions when incoming emails match conditions,' with a specific verb and resource. It distinguishes from sibling tools like update_email_rule and delete_email_rule by focusing on creation, and lists the action types (forward, auto_reply, etc.) which further clarifies its scope.

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 context that this tool is for creating new email rules, implied by the verb 'Create.' However, it does not explicitly contrast with update_email_rule or list_email_rules, nor does it provide when-not or alternative guidance. This is clear context without exclusions.

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