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

With no annotations provided, the description carries the full burden. It discloses useful behavioral details: timezone, inclusive date range, and rate base over delivered. However, it omits default date behavior, response format, and any limitations, which for a read-only stats tool is a moderate gap.

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 a single dense sentence that efficiently lists all metrics and constraints. It is front-loaded with the metric list and contains no extraneous wording.

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?

The description covers the main aspects: metrics, date range, and rate basis. However, it does not explain what happens when both dates are omitted, whether results are aggregated or per-day, or the exact response structure. Given the lack of output schema and annotations, this is somewhat incomplete.

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 coverage is 100% with basic date descriptions. The description adds meaningful semantics by clarifying the range is inclusive and uses the account's timezone, which goes beyond the schema and helps the agent understand how from/to are interpreted.

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 returns global account metrics (sent, delivered, opened, clicked, unsubscribed, bounced, new contacts) over a date range, and specifies rates are over delivered. It distinguishes from campaign-level tools by emphasizing 'cuenta' (account) but doesn't explicitly name an alternative like get_campaign_stats.

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 implies usage for account-wide metrics but does not explicitly state when to use this vs. campaign-specific tools, nor does it mention alternatives or exclusions. The context is clear but lacks explicit routing.

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