list_emails_metadata

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint false. The description adds meaningful behavioral context by emphasizing 'without body content' (privacy/performance implication) and by indicating that email_id is intended for a subsequent get_emails_content call. This provides more than the annotations alone, though it doesn't cover pagination or filtering behavior explicitly.

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, the first front-loaded with the core action and scope, the second providing a crucial linkage to another tool. No filler, no redundant restatement of schema or annotations.

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 has 16 parameters and an output schema, the description does not need to explain filtering or return details. It covers the essential purpose and the relationship with get_emails_content. A minor gap is the absence of any hint that the tool supports rich filtering, but the schema fully covers that, so the description is sufficiently complete.

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 baseline is 3. The description adds limited semantic value by naming the returned fields (email_id, subject, sender, recipients, date), which implicitly clarifies the meaning of email_id as the key for later content retrieval. It does not explain any specific parameter behavior, but the schema already does that thoroughly.

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 uses a specific verb ('List') with a clear resource ('email metadata') and enumerates the exact fields (email_id, subject, sender, recipients, date). It explicitly distinguishes itself from content-fetching tools by stating 'without body content' and references get_emails_content, making its purpose unmistakable.

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 clearly indicates when this tool is appropriate (for metadata, not body content) and even specifies a follow-up workflow ('Returns email_id for use with get_emails_content'). It does not explicitly state when not to use it or compare it with sibling tools like list_mailboxes, but the context is strong enough for an agent to infer the primary use case.

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