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

readOnlyHint=true already tells the agent this is a safe, non-mutating read. The description adds value by disclosing the payload fields (tag, digest, pushedAt, sizeBytes) in the absence of an output schema, but says nothing about paging behavior beyond what the params imply or about ordering.

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 scope and returned fields are front-loaded with no filler. The trailing 'Depot: build.v1 RegistryService/ListImages' is boilerplate but low-cost.

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 read-only list tool with a fully documented schema and readOnlyHint covering safety, the description supplies the one thing structured data lacks: the shape of the returned records. Little else is needed.

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 100% and all three parameters are documented in the schema (page_size range, page_token cursor semantics, project_id provenance). The description adds no parameter meaning, 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 ('List') and resource ('images stored in a project's Depot Registry') and enumerates the returned attributes (tag, digest, pushedAt, sizeBytes). The registry scope is distinct from CI/build/project siblings, though it never names a sibling to differentiate against.

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?

No guidance on when to use this versus depot_list_builds or the CI listing tools. The only implied usage is 'list images in a project,' and there are no prerequisites, exclusions, or alternative-routing hints.

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