Unread digest

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

An already carry safe annotations (readOnlyHint, idempotentHint), so the description doesn't need to restate them. It adds useful behavioral context beyond annotations: the tool is designed to be a cheap, single-call digest that returns previews only. This distinguishes it from alternatives and hints at resource characteristics without contradicting any annotation.

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 two concise sentences. The core purpose is front-loaded in the first line, and the second line adds routing guidance without any fluff. Every word earns its place.

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 this is a zero-parameter tool with a full output schema and clear annotations, the description is mostly complete. It covers purpose, usage context, and cost tradeoff. It doesn't detail what constitutes a 'latest preview' or how rooms are sorted, but the output schema are available to an agent, so this is a minor gap rather than a blocking one.

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?

With zero parameters, there is no param information to provide, and the baseline for zero parameters is 4. The description doesn't need to elaborate on param semantics because there are none, and the schema fully covers this aspect at 100% coverage.

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 opens with a clear, specific verb+resource stamenent: 'Unread rooms with latest preview in one call.' It directly distinguishes itself from unread_full by noting that it returns only previews, not full message bodies, which eliminates ambiguity about what the tool does.

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 explicitly frames the tool as the 'Cheapest what is unread check' and instructs users to choose unread_full instead when they need full message bodies. This gives a clear when-to-use and when-not-to-use rule, naming the alternative and the condition that selects it.

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