Set the preferred Assist pipeline

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

Mentions the underlying WS call and what it returns, which adds some context. However, annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, covering the key behavioral traits. The description doesn't add much beyond that – no mention of permissions, side effects, or whether the previous preference is lost.

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 short sentences, each earning its place: statement of purpose, WS endpoint, usage guidance, return value. Front-loaded with the action.

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?

Given a simple single-parameter mutation with full schema coverage and an output schema, the description is nearly complete. It mentions return value despite the output schema, which is slightly redundant, but otherwise nothing an agent needs 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 coverage is 100%, so the parameter is fully documented in the schema. The description doesn't add syntax or constraints beyond what the schema provides. Baseline 3 is appropriate.

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: 'Set the default Assist pipeline, used when no pipeline is specified.' The WS endpoint reference adds precision, and it clearly distinguishes itself from voice_list_pipelines.

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 explicit 'Use when:' and 'Not for:' guidance, naming the alternative tool (voice_list_pipelines) for the read 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.