Plan: change a Google Ads daily budget

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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description does not contradict them — it plans rather than mutates. Beyond that it discloses what happens at call time: the current budget and currency are read first, the policy caps the value (max_daily_budget_micros in cap_currency, +20% per 24h), a human approval is required downstream, and a shared budget affects every campaign using it.

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?

Four dense sentences, front-loaded with the amount/semantics and target selection, then policy and approval behavior. Little waste, though the micros conversion example duplicates what the schema already states.

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 planning tool with no output schema, it covers target selection, unit semantics, policy caps, approval flow, and shared-budget side effects. It stops short of telling the agent how to inspect the resulting plan (plan_get/plan_list) or whether the plan expires, which would complete the loop.

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 the baseline is 3, but the description adds real meaning: it explains the micros unit against the account currency with a worked example, and clarifies the either/or relationship between budget_id and campaign_id that the schema presents only as two loosely described fields. The currency/micros example partially repeats the schema, keeping it out of 5 territory.

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: 'Plan a new daily amount for one Google Ads campaign budget'. It also explicitly distinguishes itself from the apply step ('a human approval is required before gads_apply'), so an agent can tell this planning tool apart from its sibling execution tools without opening a 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?

Gives concrete targeting guidance ('Give budget_id, or campaign_id to change the budget that campaign uses') and names the follow-up alternative gads_apply along with the approval gate that separates planning from execution. The conditions for use are explicit rather than inferred.

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