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

Annotations already declare destructiveHint=true, idempotentHint=false, readOnlyHint=false. The description adds real value beyond them: the confirm preview/apply gate, which the annotations never mention, plus the bid>0 constraint and status enum. It still doesn't say what is destroyed or whether existing values are overwritten, so 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?

Two tight sentences, front-loading the mutation and constant constraints before the confirm gate. No filler; every clause earns its place.

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?

Output schema exists so return values need not be described, and annotations cover the safety profile. The description adds the crucial confirm-gate semantics and value constraints. It remains slightly thin on identifier parameters, but for this mutation complexity it is largely complete.

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 must carry the parameter burden. It meaningfully documents three of seven params (bid>0, status Active|Paused, confirm preview/apply), but account_id, ad_group_id, keyword_id, and customer_id are left unexplained. Partial compensation for a 0% coverage schema lands at 3.

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 (updates) and a specific resource (a keyword) plus the two mutable fields (bid, status). An agent can distinguish this from read siblings like list_microsoft_keywords or add_microsoft_keywords. It stops short of naming a sibling alternative, keeping it at 4 rather than 5.

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?

Provides concrete usage rules: bid must be >0, status accepts Active|Paused, and confirm=false previews while confirm=true applies. This tells the agent when/how to invoke the write. It does not name an alternative tool or state prerequisites (e.g., where keyword_id comes from), so not a 5.

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