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

Adds context beyond the annotations: raising the bid returns a preview and requires confirm=true, which tells the agent that a raise is a two-step operation while implying a lower is applied directly. The units are clarified as account currency. It does not state what the preview looks like or whether a confirmed raise is reversible, which is a gap for a destructiveHint=true tool, but the key behavioral wrinkle is disclosed.

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. The precondition and the units constraint are front-loaded and the preview/confirm mechanic follows immediately; nothing repeats the title or the annotations.

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 six-parameter mutation tool with no output schema, the description covers the bid semantics and the confirm gate but leaves account/folder scoping and the adgroup identifier unexplained. Adequate to call the tool safely, not complete enough to predict the result of a confirmed change.

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 50%. The description meaningfully explains 'bid' (account currency) and 'confirm' (needed when raising), which are the two parameters the schema leaves bare. It says nothing about 'adgroup' (the required identifier) and only implicitly relies on the schema descriptions for folder/account/language.

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?

Names a specific verb and resource: 'Change the bid or cost cap ... of an ad group', and scopes it to ad groups on manual bidding. The platform prefix and 'bid or cost cap' wording separate it from tiktok_update_budget and the other platform update tools, though it never names those alternatives 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?

'an ad group that uses a manual bid' is a genuine applicability precondition that rules out auto-bid ad groups, which is real when-to-use guidance. It stops short of naming the alternative tool to use for budget changes or for ad groups on automatic bidding, so an agent must still infer that routing.

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