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

readOnlyHint=true already declares the safety profile, so the description's added value is the Space-scoping behavior: reads are confined to the active Space and space_id overrides for a single call only. It adds nothing about freshness/latency of coverage data, permissions, or result shape beyond the conceptual list of what the tool reports.

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, no filler, with the core 'what data' clause front-loaded and the scoping caveat placed second. The first sentence is a dense three-part list, which is efficient but slightly hard to parse on a first read.

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 two-parameter read-only lookup with no output schema, the description effectively pre-describes the return content by naming the three coverage questions it answers. The only real gap is the opaque business_id, which matters because coverage is presumably per-business.

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 coverage is 100%, so both parameters are documented structurally and space_id even explains the override semantics. The description only restates the space_id override and says nothing about business_id beyond what the schema offers ('The business id.'), leaving unclear whether that is the advertiser's business or a competitor's.

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 enumerates the exact content returned: which public ad library covers each connected platform by region, which platforms lack a library, and the source of auction data. That is a specific resource shape distinguishable from siblings like get_competitor_allowance or get_competitor_auction. It never explicitly contrasts itself with those siblings, which keeps it off 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?

It gives a real usage rule for Space scoping and points to set_active_space as the switching mechanism, plus the space_id one-call override. It never says when to call this versus the other competitor data tools (get_competitor_auction, find_competitor_library_accounts), so selection between siblings is left to inference.

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