messages_chats

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the description needn't restate safety; it instead discloses two non-obvious traits: the response carries no message content, and the tool requires Automation permission to be granted in Messages. It does not mention limits, pagination, or ordering of the returned conversations.

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?

Three short clauses, each carrying distinct information: what it returns, what it does not do, and what permission it needs. Nothing is repeated from the annotations or schema, and the scope statement leads.

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 zero-parameter read-only listing tool with an output schema, the description covers scope, exclusions, and the auth prerequisite. The only remaining gap is volume/ordering behavior (how many conversations come back), which matters for an agent deciding whether to page or narrow the call.

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?

The tool takes zero parameters, so the baseline of 4 applies. The description correctly describes the output fields ('id + name'), which is a bonus rather than a substitute for parameter documentation.

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 and resource ('List Messages conversations') and bounds the payload ('id + name'), which is enough to separate it from content-fetching siblings like message_body. It does not name the alternative tools (messages_search, messages_with) explicitly, 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 content; sending isn't supported' sets clear boundaries and implies this is a discovery/enumeration step rather than a search or send operation. It adds the precondition 'needs Automation access for Messages', which is actionable guidance an agent must have before calling.

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