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

readOnlyHint=true already establishes the safety profile, so the description earns credit by disclosing the exact return payload (status, timestamps, duration, time saved, cached/total step counts) — the only place return values are described since there is no output schema. It does not mention error behavior for a missing build_id, which keeps it short of 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: the substantive content is front-loaded, and the trailing API provenance note ("Depot: core BuildService/GetBuild.") is low-value but brief and harmless.

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?

With no output schema, the description must carry the return-value burden and it does, listing the salient result fields. For a single-parameter read-only tool with full schema coverage, the remaining gap (what happens when the build doesn't exist) is minor.

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% and the single build_id parameter is already documented in the schema as coming from depot_list_builds. The description adds no extra semantics about the identifier format or constraints, so the baseline 3 applies.

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 ("Get one container build") and enumerates the fields returned (status, timestamps, duration, time saved, step counts). The word "one" implicitly distinguishes it from depot_list_builds, but no sibling is named explicitly.

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 contains no when-to-use guidance, no prerequisites, and no comparison to alternatives such as depot_list_builds, depot_get_build_steps, or depot_get_build_step_logs. The only routing hint lives in the schema ("from depot_list_builds"), not in the description.

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