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

Discloses it returns summaries, long-poll behavior, and cursor usage. Since no annotations, description carries burden; it adequately covers read-only nature and key behaviors, though missing pagination details.

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, front-loaded with purpose and return fields, followed by usage tips. No redundant information, every sentence 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?

Covers key behaviors: return summaries, long-poll, cursor. Missing pagination or limit information, but sufficient for a simple list tool with well-documented parameters.

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 has 100% coverage, baseline 3. Description adds context for 'wait' and 'since' usage but does not enhance 'match' parameter beyond schema. Minimal added value over 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 explicitly states the tool lists messages in an inbox and specifies the returned fields (id, from, subject, received_at, tls). It clearly distinguishes from sibling get_message by noting it returns summaries.

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?

Provides guidance on when to use long-poll (wait parameter) and cursor usage (since). Differentiates from get_message for full body retrieval. Does not explicitly state when not to use, but context is clear.

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