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

Annotations already mark it read-only and non-destructive, and the description adds real behavioral detail: SB results are [range_start, range_end] with range_start as effective CPC floor; SP covers manual keywords and auto targeting groups; unsupported campaign types produce a warning; and the underlying reason is disclosed (no vCPM bid-rec API). This exceeds what structured fields alone convey.

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 dense but every sentence earns its place: core purpose, SB/SP behavior, usage timing, and vCPM exception are each covered without dangling filler. Key constraints like 'NOT valid for' and 'needs ad_group_id' are front-loaded or highlighted.

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 tool with no output schema, the description covers a lot: return format for SB, warning behavior, valid/invalid campaign types, and SP targeting inputs. The main gap is ad_format, an undocumented enum that is not mentioned in the description, leaving the agent to guess how it applies. Otherwise the tool is well-specified.

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 description adds meaning for auto_targets by listing the four targeting groups, explains ad_group_id's conditional requirement, and clarifies that keywords refer to manual keywords. However, ad_format remains undocumented in both the schema and the description, and its role in SB productCollection/video vs SP is not explained. That keeps this from being a 5.

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 description opens with a specific verb and resource: 'Amazon's suggested bid + range per keyword for a SPECIFIC campaign', and immediately distinguishes SB vs SP behavior. It makes clear this is a bid-recommendation retrieval tool, not a general campaign report or budget tool, and differentiates it from alternatives by routing campaign types.

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 explicitly says 'Check this BEFORE choosing bids', which tells the agent when to call it. It also explicitly states what it is NOT valid for (BRAND_IMPRESSION_SHARE/vCPM campaigns) and names the alternative round-trip pattern via KEYWORD_INVALID_BID. The ad_group_id condition is also provided as a usage rule.

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