Message Update

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

Annotations already declare the read/write and idempotency profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false). The description adds real context beyond them: partial-update semantics ("Only provide fields to change") and the sent-message immutability constraint. It stops short of describing permissions or success behavior.

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?

Two tight sentences: purpose and editable fields first, then the two constraints. Nothing is padded or redundant.

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 mutation tool whose annotations already carry the safety profile and whose schema fully documents all six parameters, the description covers the essential behavior (partial update, sent-message immutability). Nothing critical for correct invocation is 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 description coverage is 100%, so every parameter is already documented in the schema. The description corroborates the field list and adds the partial-update instruction, but introduces no syntax or format detail beyond the schema. 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 (Edit) and resource (draft or internal note) and enumerates the mutable fields (text, subject, language, translation). It does not name sibling tools like message_send or message_delete, so it is clear but lacks explicit 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?

Good context: "before it is sent" sets the lifecycle window, and "Sent messages cannot be edited" is an explicit when-not condition. It does not, however, point to an alternative (e.g. resend/new message) for already-sent messages.

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