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

Annotations already cover the safety profile with readOnlyHint=true, so the description is free to add genuinely new context: default ordering ('active first'), the per-ad payload fields, the epistemic caveat that library data shows publication not performance, and how space scoping behaves for this call. It omits pagination/default-limit behavior, which matters at a 500 max.

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 front-loaded sentences with no filler: purpose and payload first, the interpretive caveat second, the scoping mechanics last. Each sentence carries distinct information an agent needs, including the return shape, which matters since there is no output schema.

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?

With no output schema, the description correctly spends words on what each ad returns and the ordering. It is nearly complete for a read-only list tool, with the main residual gap being pagination and how limit interacts with the 'active first' ordering.

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?

At 67% schema description coverage, the schema already documents space_id, source_id, angle_type and competitor_id. The description reinforces the space_id override semantics but adds nothing for limit, status, or source_id ('One library.' is opaque in both places). Baseline 3 is appropriate — the description neither compensates for the gaps nor contradicts 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?

Names a specific resource with scope: ads a competitor published in public ad libraries, including what each record carries (library, dates, angle type, offers in copy). It implicitly separates itself from get_competitor_offers by noting offers come from the ad copy, but it never names a sibling tool as an alternative, so it falls short of a 5.

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?

Gives a clear interpretive constraint ('library data shows what a competitor published, never what worked') that tells the agent when this data is and isn't appropriate. It also resolves the space ambiguity by naming set_active_space as the switching mechanism versus the space_id per-call override. No explicit when-not-to-use guidance against related competitor tools like get_competitor_coverage or get_competitor_auction.

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