update_message

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

With no annotations, the description carries the full burden. It does disclose important behavioral traits: partial updates ('pass only the fields you want to change'), restore semantics, and the ability to move into or out of a folder. It omits auth permissions, return value, and failure behavior, so it is adequate but not rich transparency.

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 sentences with no filler. The core action and the key behavioral nuance ('pass only the fields you want to change') are upfront, and the list of supported operations is compact yet complete.

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?

Given five parameters, no output schema, and no annotations, the description covers the tool's core purpose, supported operations, and partial-update behavior well enough for an agent to call it correctly. Minor gaps remain around return values and prerequisites, but these are less critical for a state-update 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 coverage is only 60%, leaving 'read' and 'flagged' without schema descriptions. The description compensates by explaining the boolean meanings as mark/unread and flag/unflag, and it adds the partial-update semantics that apply to all parameters. It also aligns with the restore and folderId descriptions in 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?

The description uses a specific verb and resource ('Update a message's state') and immediately enumerates the exact supported operations: read/unread, restore, flag/unflag, and folder moves. It clearly distinguishes this tool from siblings like delete_message, get_message, and send_email by scoping it to in-place state mutations.

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 gives clear context for when to use the tool: any time you need to change message state, and it notes that multiple changes can be combined in one call. However, it does not explicitly mention when not to use it or point to alternatives for related operations like deletion or sending.

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