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

Annotations only tell the agent this is a non-read-only, non-idempotent, open-world write; the description adds the genuinely important trait that currency and time zone can NEVER be changed after creation, which is a permanent consequence not encoded anywhere in the structured fields. It stops short of describing success output or auth/permission requirements.

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, both load-bearing: the first names the action and scope, the second front-loads the irreversible constraint before the confirmation instruction. No filler.

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 create tool with no output schema, the description covers the main risk an agent needs to know before calling. It could say more about what creation returns (a new account/customer ID) or required permissions, but nothing critical to correct invocation 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?

Schema coverage is 60%, and the two undocumented parameters (time_zone, currency_code) are exactly the ones the description clarifies as immutable. That adds meaning the schema does not carry — notably that the defaults (America/Denver, USD) are effectively permanent choices.

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 and resource ('Create a new Google Ads account') plus the scope ('for a client under your manager account'), which cleanly separates it from create_client, ga4_create_property, and link_account in the sibling set. An agent can identify what this does without opening the schema.

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 one concrete prerequisite — confirm currency and time zone with the human before creating — which is real usage guidance. But it never states when to reach for this tool versus neighbors like create_client or link_account, so tool-selection routing 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.