Unread DM count

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description's read-only nature is consistent. The description adds the 'cheap check' performance hint and the 'authenticated account' scoping, which is useful but minimal. It doesn't describe response format or edge cases, but output schema covers returns. With annotations present, the bar is lower; the description adds modest value beyond them.

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, well-structured sentence that front-loads the core function ('Return how many direct messages are unread') before the contextual rationale. Every word earns its place; no redundancy or filler.

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 tool with no parameters, existence of an output schema, and annotations covering safety, the description is adequate. It states what it does and when to use it. It lacks explicit alternatives or caveats, but those are not critical given the tool's simplicity. A 5 would require more guidance, but this is solid.

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 has zero parameters, and schema coverage is 100% (empty schema). Per guidelines, baseline is 4 for zero-parameter tools. The description adds no parameter info, which is fine because there are none to explain.

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 states a specific verb ('Return') and resource ('unread direct message count for the authenticated account'), which clearly distinguishes it from siblings like get_unread_notifications_count. It also frames the tool as a cheap pre-check before listing conversations, adding context that differentiates its purpose.

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?

It provides a clear usage context: 'a cheap check before listing conversations' tells the agent when to call this tool. It does not explicitly exclude other tools or name alternatives, but the implication is strong enough for a simple read tool. Missing explicit when-not-to-use guidance, so not a 5.

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