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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the tool returns recent messages with specific fields, which is useful, but lacks details on permissions, rate limits, error conditions, or whether it's read-only (implied but not explicit). For a tool with zero annotation coverage, this is a significant gap in 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?

The description is concise and front-loaded, consisting of two clear sentences that directly state the tool's action and return value. There is no wasted language or redundancy, making it efficient and easy to parse.

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 the tool's moderate complexity (2 parameters, no output schema, no annotations), the description is minimally adequate. It covers the basic purpose and return fields, but lacks details on usage context, behavioral traits, or error handling. Without annotations or output schema, it should do more to compensate, but it meets the bare minimum for a read operation.

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 description coverage is 100%, so the schema already documents both parameters ('limit' and 'address') with details like defaults and examples. The description adds no additional parameter semantics beyond what's in the schema, such as clarifying the 'address' format or 'limit' implications. Baseline 3 is appropriate when the schema does the heavy lifting.

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 clearly states the tool's purpose: checking an inbox for an @agentlair.dev email address and returning recent messages with specific fields (sender, subject, received time). It uses specific verbs ('check', 'returns') and identifies the resource (inbox for @agentlair.dev addresses). However, it doesn't explicitly differentiate from sibling tools like 'read_message' or 'list_addresses', which prevents a score of 5.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing a claimed address), exclusions, or comparisons to siblings like 'read_message' for detailed content or 'list_addresses' for address management. This leaves the agent without context for tool selection.

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