ads_changes

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

With no annotations provided, the description carries the full burden, and it delivers: it declares read-only, states Google's 30-day and 10,000-row retention limits, and warns that empty results over longer windows are limits rather than findings. It also discloses the filtering quirk about resourceType vs. changed field names, which an agent could not infer from the schema alone.

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?

Three sentences, each earning its place: purpose and content, retention-limit caveat, and filtering guidance. The most important information is front-loaded, and the read-only note closes it without redundancy.

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 tool with two self-describing parameters and an output schema, the description covers purpose, scope, behavioral limits, filtering semantics, and sibling relationship. Nothing an agent needs in order to decide when and how to call this tool 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?

The input schema already describes both parameters with 100% coverage, so the baseline is 3. The description adds meaningful value beyond the schema by explaining how the days parameter interacts with Google's retention limit and by clarifying the correct filtering approach (resourceType, not changed field names) even though those details are not directly schema properties.

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 opens with a specific verb and resource ('Read the Google Ads change history') and details what the history contains: what changed, when, fields, by whom, and source. It distinguishes itself from sibling data tools by explicitly positioning itself as the audit trail for ads_update writes, so an agent can tell it apart from ads_campaigns or ads_keywords.

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 makes the intended use clear: consult this tool when you need the change/audit history rather than the current state, and it explicitly notes it is the audit trail for anything ads_update writes. It gives practical guidance on interpreting empty results over long windows and how to filter. It does not explicitly name alternatives to use instead for current data, but the context is clear enough.

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