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

Annotations already declare readOnlyHint=true, so safety is covered; the description adds genuinely new behavioral context: results are scoped to the active Space session binding, and space_id overrides it for this call only without mutating the session. Only pagination/return-format detail (beyond what schema and meta.nextCursor already imply) is absent.

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 dense sentences with zero waste; the primary scope rule comes first, followed by the Space-override mechanics. Nothing is repeated verbatim from the 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?

For a read-only list tool with fully documented parameters and no output schema, the description covers scope, session behavior, and override path—enough to invoke correctly. Return shape and pagination handling are only indirectly covered via the cursor parameter.

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 limit, cursor, space_id and campaign_id are all documented in structured data. The description adds only a light usage hint that campaign_id narrows to one campaign, which the schema already states — baseline 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?

States a specific verb+resource ("List ad groups") and defines scope precisely: all visible campaigns, or narrowed to one via campaign_id. This distinguishes it from get_ad_group (singular) implicitly, though it never names a sibling explicitly.

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?

Explains how to narrow scope with campaign_id and where the data comes from (the active Space), and names the alternative mechanism for changing scope — set_active_space — or the per-call space_id override. Clear context, but no explicit when-not-to-use guidance.

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