Estimate a Reddit ad group

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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with 'read-only' and 'Nothing is created.' It goes further by disclosing output semantics: fixed 30-day audience basis, default schedule of tomorrow for 30 days, and bid range for bid_type in account currency. This gives the agent useful behavioral detail beyond the structured fields.

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?

The description is compact, front-loaded with the core purpose, and every sentence adds value. It covers inputs, outputs, defaults, and side effects in three sentences with no redundant phrasing.

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 complex 19-parameter tool with no required fields, the description provides the essential contextual pieces: what the tool does, when to run it, what inputs to reuse, what outputs to expect, and that no changes are made. The presence of an output schema covers return-structure details, so nothing critical 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 description coverage is 0%, so the description carries the burden of explaining semantics. It compensates by grouping the 19 optional parameters into meaningful categories: 'same targeting and budget', schedule defaults, and bid_type. It does not document each optional field individually, but the grouping plus self-explanatory parameter names provides a solid practical understanding.

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?

The opening sentence states exactly what the tool produces: audience size, delivery estimate, and Reddit's suggested bid for a planned ad group. It distinguishes itself from siblings by explicitly naming estimate_budget as its counterpart and draft_reddit_ad_group as the later step. The read-only qualifier and 'Nothing is created' further disambiguate it from drafting and mutation tools.

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 gives explicit sequencing guidance: 'run it before draft_reddit_ad_group with the same targeting and budget.' It also names the closest sibling alternative, estimate_budget, so an agent knows this is the Reddit-specific equivalent. This is actionable and leaves little to inference.

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