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

Annotations already declare readOnlyHint=false and idempotentHint=true, so the safety profile is covered; the description goes further by explaining the operational consequence of spendCap — Meta's hard stop that halts all ad delivery once the cap is reached — and how to clear it with null. It still omits permission/auth requirements and what the update returns, but the added semantic warning is substantive and nothing contradicts the annotations.

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 tight sentences, each earning its place: the capability is front-loaded and the consequential caveat follows. No filler or restatement of the tool name.

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 5-parameter mutation tool with no output schema (so return values needn't be described), the description covers the semantics that matter and the annotations cover idempotency and open-world scope. It does not say whether name and spendCap can be updated together or that adAccountId is the sole required 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 only 40%, so the description must carry weight, and it does the most important lifting: spendCap is 'whole currency units' and null 'removes the limit,' which is not stated in the schema. It leaves name (1-100 chars) and the act_\d+ format of adAccountId unaddressed, but the highest-risk parameter is well explained.

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 specific verbs and the exact resources it mutates: the account's name and its spending limit (spendCap). This cleanly separates it from ads_get_account (read), ads_create_account (create) and ads_set_status (status changes only), so an agent can pick it 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?

The description enumerates the two editable fields but gives no when-to-use guidance, no prerequisites, and never names an alternative (e.g. ads_set_status for delivery status, ads_create_account for provisioning). Usage must be inferred entirely from the field list.

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