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

Annotations already flag this as a destructive write (destructiveHint=true, readOnlyHint=false). The description adds real behavioral value: it warns that re-creating the 4 AUTO matching groups on an existing campaign yields INVALID_ARGUMENT, preventing a likely failure. It does not cover auth/prerequisites beyond what the schema's confirm_id implies, hence not a 5.

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?

Front-loaded with the core action, and every subsequent sentence carries decision-relevant detail (mode payloads, error pitfall, alternative tool). It is dense rather than padded, though the bilingual phrasing and long parentheticals make it slightly heavier than necessary.

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 destructive write tool with no output schema, the description equips an agent to call it correctly: it defines both payload variants, the enum meanings, and the key failure mode. It leaves the confirm_id two-step flow to the schema, which is acceptable since the schema documents it.

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?

The schema types 'targets' only as an untyped array at 67% coverage, so it carries little meaning. The description compensates strongly by spelling out the exact object fields for both MANUAL (campaign_id, ad_group_id, bid, asin/category_id/expression) and AUTO (auto_match) targets, including the semantics of each auto_match enum value.

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 SP targets') and then clearly distinguishes the two operating modes (MANUAL vs AUTO) with distinct payload shapes. An agent can immediately tell what this creates and how it differs from sibling list/update/delete target 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?

Explicitly covers when to use it, when NOT to use it (existing AUTO campaigns already have the 4 groups), and names the correct alternative path (ads_list_sp_targets + ads_update_sp_target_bid) for the bid-only case. This is textbook routing guidance.

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