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

There are no annotations, so the description carries the full burden. It correctly indicates a read-only list operation and adds a useful nuance about the optional ad_account_id behavior. It does not mention side effects, authentication, or return format, but for a simple list tool these are not critical. The added nuance about omitting the account ID when there is exactly one account demonstrates proactive disclosure.

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 four short sentences with zero redundancy. The core purpose is stated first, followed by usage context, a parameter nuance, and a sibling distinction. Every sentence adds value and nothing is extraneous.

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's simplicity (2 parameters, no output schema, no nested objects), the description covers the essential aspects: what it does, when to use it, a parameter behavior, and how it differs from a sibling. It does not describe the return format, but that is implied by 'List campaigns'. The absence of an output schema does not require explanation, and the tool is not complex enough to need more context.

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% – both companyId and ad_account_id have descriptions. The tool description adds only a restatement of the ad_account_id condition ('Omit ad_account_id when the connection has exactly one ads account'), which is already in the schema. It does not add new semantic value beyond the schema, so the baseline 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 'List campaigns in an X ads account' – a specific verb, resource, and platform. It also explicitly distinguishes from 'list_ad_campaigns (Meta)', which resolves ambiguity with a similarly named sibling tool. No other tool in the sibling list has the same purpose.

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 provides a direct usage condition: 'Use when the user asks what X/Twitter ads are running.' It also gives explicit parameter guidance ('Omit ad_account_id when the connection has exactly one ads account') and names the alternative ('Distinct from list_ad_campaigns (Meta)'), effectively telling the agent when NOT to use this tool. This is comprehensive.

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