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

Annotations already declare readOnlyHint/idempotent/non-destructive, so the safety bar is lower. The description adds real behavioral context beyond them: the strictest answer across all recipients wins, the answer depends on which app is calling, and source is auto-filled for message_send/note_write/slack_post. That is meaningful extra disclosure.

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?

Purpose is front-loaded in the first sentence, followed by parameter semantics and the auto-fill note. Every sentence carries information; there is no filler or redundancy.

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?

With an output schema present, return values need not be described. The description covers the prediction semantics, the relevant input parameters, and the auto-fill behavior, leaving nothing essential for a correct call missing.

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 0%, so the description must carry parameter meaning, and it largely does: `to` spans To/Cc/Bcc with strictest-wins semantics, `account` is the sending account name or address, `label` is something like 'Clients', and `source` is auto-populated for specific actions. Only the required `action` parameter is left implicit.

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?

States a specific verb+resource: predict what a policy decision 'would happen if you tried an action now, and why, before trying it.' This dry-run framing is clear and distinct in spirit from a plain lookup, but the description never names the closest siblings (check_permissions, get_policy, explain_access), so differentiation is left to inference.

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?

'before trying it' implies the moment of use (dry-run ahead of a real action), which is useful context. But no explicit guidance on when NOT to use it or how it relates to check_permissions/get_policy/explain_access, so the agent must infer the routing.

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