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

Annotations already declare readOnlyHint=true and destructiveHint=false, so no safety contradiction exists. The description adds useful behavioral context beyond annotations, such as the fields returned and that budgets are in 'major currency units,' and it highlights the ad_account_id omission rule for single-account connections.

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 carry all essential information with no filler. The main action and returned data are front-loaded, followed by a crisp usage cue and the key edge-case instruction.

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 read-only listing tool, the description covers when to use it, what fields are returned, the budget unit nuance, and the ad_account_id edge case. Combined with full schema documentation and safety annotations, nothing essential is missing for an agent to call it 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?

Schema description coverage is 100%, so the schema fully documents all three parameters. The description reinforces the ad_account_id omission rule but does not add meaningful parameter details beyond what the schema already provides, matching the baseline for full schema coverage.

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 names a specific verb and resource ('List campaigns in a Meta ad account') and enumerates the returned fields: status, objective, budgets, and schedule. Mentioning Meta and Facebook/Instagram clearly distinguishes it from sibling tools like list_x_ad_campaigns, so an agent can select it correctly without opening schemas.

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 gives explicit guidance: 'Use when the user asks what ads/campaigns are running on Facebook or Instagram.' This provides clear context for when to invoke the tool, though it does not explicitly name alternatives or state when not to use it.

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