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

Annotations already declare it is a non-readonly, non-destructive, non-idempotent mutation, so the bar is lower. The description adds real value beyond them: the auth requirement (`full_access` key) and the state precondition that the email must still be scheduled, which implies a failure mode for already-sent emails. It does not describe what happens on failure or what the response contains.

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?

Three short lines, front-loaded with the purpose, then the constraint, then the auth/API detail. Every sentence carries distinct information with no padding.

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?

No output schema exists, so the description would ideally hint at the return value, and it does not. Otherwise it covers purpose, precondition, and auth for a simple two-parameter PATCH, which is sufficient to invoke correctly.

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 both `id` and `scheduled_at` are fully documented including format, examples, and the 30-day limit. The description adds no parameter-level detail beyond mapping the operation to `scheduled_at`, so the baseline 3 applies.

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 (reschedule) and resource (email), then immediately narrows the scope to changing `scheduled_at` on an email that is still `scheduled`. That precondition plus the verb makes it clearly distinguishable from cancel_email, send_email, and get_email without opening any schema.

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?

Gives the key usage gate: the email must still be in `scheduled` state, and a `full_access` API key is required. It does not explicitly name the alternative tool (e.g. use cancel_email to stop it entirely), which keeps it below a 5.

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