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

The description adds the constraint that updates happen before sending, which is useful behavioral context. Annotations already declare readOnlyHint=false and destructiveHint=true, so the description need not restate that; however, it does not disclose whether only provided fields are updated or what happens if the message is already sent. It does not contradict annotations.

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, focused sentence that front-loads the verb and resource. It is concise, with no wasted words, and is easy to parse quickly.

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 10 parameters and no output schema, the description is extremely brief. It does not explain what 'partially update' means, which fields are typically changed, or any limitations or prerequisites. While annotations provide some safety context, the description leaves significant gaps for an agent to correctly invoke the tool.

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 60%, and the description provides no parameter details. Several parameters (id, cc, bcc, subject) lack schema descriptions, and the tool description does not compensate. It adds no meaning beyond what the schema already provides, so it fails to clarify the less-documented fields.

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 a specific verb ('update'), resource ('scheduled message'), and the qualifier 'partially', which distinguishes it from full-update tools like hires_update_message. It also adds a temporal constraint ('before it is sent') that clarifies 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 implies usage for partial updates on scheduled messages, but it does not explicitly state when to prefer this over alternatives or when not to use it (e.g., after the message is sent). It offers no exclusions or comparisons, leaving guidance to inference.

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