get_unread_emails

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

With no annotations provided, the description carries the behavioral transparency burden. It adds context about the optional mailbox filter and the use case, but does not disclose other behaviors such as whether the operation is read-only, how results are sorted, or the response format. However, the tool name and nature strongly imply a read-only operation, so this is not a major risk. The description gives some context but lacks depth.

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 sentences, concise, and front-loaded. It states the primary action first, then the usage context, then the alternative exclusion. Every sentence earns its place with no repetition or fluff.

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 simple read tool with two optional parameters, the description covers the core purpose, usage context, and alternatives. It does not describe the return structure, but no output schema exists and the tool's behavior is fairly predictable. It could mention sorting or pagination, but these are not essential for correct invocation. Overall, it is complete enough for an agent to select and call the tool correctly.

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 input schema already covers both parameters (limit and mailboxId) with full descriptions (100% coverage). The description's phrase 'optionally filtered by mailbox' aligns with the mailboxId parameter but adds no new information about limit or parameter syntax. Since the schema does the heavy lifting, a baseline score of 3 is appropriate.

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 function: 'Retrieve unread emails, optionally filtered by mailbox.' The verb 'Retrieve' combined with the resource 'unread emails' is specific and unambiguous. It also distinguishes itself from sibling tools by explicitly ruling out search_emails for this purpose, which differentiates it from a likely alternative.

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 explicit usage guidance: 'Best for checking what needs attention' indicates when to use it, and 'Do not use search_emails for this purpose' explicitly excludes the most likely alternative. This is a clear directive that helps an agent choose this tool over search_emails.

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