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

Beyond the readOnlyHint and idempotentHint annotations, the description adds genuinely useful behavioral context: stats update in real time as Meta webhooks arrive, and recent_errors only appears when sends have failed, capped at 5 distinct reasons. This helps the agent set correct expectations.

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 tight sentences: the first front-loads purpose and output fields, the second adds behavior and a conditional field. There is no filler or redundant restating of the tool name.

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 one-parameter, read-only stats tool with no output schema, the description covers the purpose, the returned fields, the live-update behavior, and the conditional error payload. Nothing needed for correct invocation or interpretation is missing.

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 0%, so the description carries no explicit parameter guidance. However, the single required campaign_id is self-explanatory and already constrained as a UUID, and the phrase 'for a campaign' connects it to the resource. This is adequate but not enriched beyond the 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 uses a specific verb-resource pair ('Get live delivery stats for a campaign') and enumerates the exact returned fields, making the tool's purpose immediately obvious. It also reads clearly against sibling tools like list_campaigns or account_status, so there is little room for confusion.

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 frames when the tool is appropriate: retrieving live, per-campaign delivery statistics. It does not explicitly name alternatives or exclusions, but the sibling list and the emphasis on 'live' stats convey the intended context strongly enough.

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