Active entities

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

The read-only nature is already disclosed by readOnlyHint=true, and the description adds no contradiction. It does clarify that the result is a set of ids in a window and constrains times to whole-hour ISO 8601, but it does not describe output shape, pagination, or how 'activity' is defined.

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 very short and front-loaded with the core purpose. Every sentence earns its place: the entity types, the workflow tip, and the timestamp constraint are all non-redundant.

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 simple read-only lookup tool with no output schema, the description gives enough to invoke it correctly: entity selection, required time window, and the whole-hour ISO 8601 constraint. It could mention response format or pagination, but the output is clearly ids and the annotations cover side-effect safety.

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?

The schema only describes account_id and leaves start_time and end_time as bare strings. The description compensates by specifying 'Times are whole-hour ISO 8601', which is essential for correct invocation. It also reinforces the entity enum by naming the three id types, though it adds no detail about relationships or bounds between start_time and end_time.

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 states exactly what the tool returns: CAMPAIGN, LINE_ITEM, and PROMOTED_TWEET ids with activity in a time window. It also signals how it relates to analytics tools by saying 'Call before analytics so you don't request empty ids.'

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 explicitly tells the agent to call this tool before analytics to avoid requesting empty ids, which is clear workflow guidance. It does not name alternative sibling list tools or exclusions, but the before-analytics directive gives enough context for selection.

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