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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds nothing beyond that: it does not say what happens if the email already sent, whether the old schedule is replaced, or what errors occur when the email isn't in a scheduled state.

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?

A single front-loaded sentence with no filler, exactly matching the action. It is efficient, though so terse that it borders on restating the title 'Reschedule Email' rather than adding information.

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 state-changing tool with no output schema, the description leaves key questions unanswered: timezone/ISO handling expectations, behavior when the email is already sent or cancelled, and whether the response confirms the new schedule. Annotations cover safety but not these operational details.

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 100%, with both `id` (em_xxx format) and `scheduled_at` (ISO 8601) fully documented in the schema. The description adds no format, constraint, or timezone guidance beyond what the schema provides, so 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 ('change the send time') and resource ('a scheduled email'), which is precise enough for an agent to know exactly what mutation occurs. It does not explicitly contrast with neighbors like cancel-email, retry-email, or get-email, so it stops short of full sibling differentiation.

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?

No guidance on when to use this versus alternatives such as cancel-email or send-email, and no stated preconditions. The word 'scheduled' hints the email must currently be scheduled, but this is left implicit rather than stated as a usage condition.

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