Messages API: Update a message

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

Annotations already declare non-readOnly, non-idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds real value with the encoding/language disclosure (values sent unchanged, Persian or Arabic-Indic digits accepted), but says nothing about permissions, side effects, or what the update returns.

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?

Front-loads the action and endpoint, then lists body fields and the encoding caveat. Each sentence carries information; the endpoint URL is verbose but legitimately precise for a client API wrapper.

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 with no output schema, the description covers inputs reasonably but omits what the response contains, what happens to unmodified message fields, and any auth requirements. Adequate but with clear gaps.

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 the schema already documents all six parameters thoroughly. The description reinforces submitted_values and extra_body and adds a genuinely useful note about Persian/Arabic-Indic digits being sent unchanged, but offers no syntax or format detail beyond the schema.

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 ('Update a message') and pins it to a concrete PATCH endpoint, so an agent can distinguish it from siblings like gapify_create_message and gapify_delete_message. It stops short of describing what aspects of a message are actually mutable beyond the submitted_values field.

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?

There is no guidance on when to update versus create/delete a message, and no prerequisites or alternative tools are named. The agent must infer usage entirely from the method name and path.

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