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

With no annotations provided, the description carries the full behavioral burden. It discloses the default ledger read path, the existence of a 'live' source, and the important limitation that manager accounts cannot be queried for metrics while enabled non-manager accounts can. This is genuinely useful behavioral context beyond the parameter schema.

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 tight sentences with no filler. The primary action and default behavior are front-loaded, and the manager-account caveat is placed directly after, making the most important information immediately visible.

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 list tool with one optional parameter and no output schema, the description is nearly complete: it identifies what is listed, the source options, and a key limitation on downstream metric use. It does not describe return fields, but that omission is minor for this level of complexity.

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 description coverage is 100% and the single 'source' parameter is already well documented with its enum and default behavior. The tool description mostly echoes that default ('Supabase ledger by default') rather than adding new parameter-level information, so the baseline of 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 the exact operation ('List'), the resource ('accessible Google Ads accounts'), and key scoping ('Supabase ledger by default'), which distinguishes it from other list tools in the sibling set. The manager-account caveat adds further specificity about what the list contains.

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 clear the default source and that manager accounts are not valid targets for metrics queries, implying when not to use this data for metrics. However, it does not name an alternative tool or explicitly state when to prefer 'live' over the ledger, so the usage guidance is implied rather than explicit.

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