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

readOnlyHint=true already establishes this as a safe read, so the bar is lower. The description adds value by naming the returned fields, but says nothing about pagination behavior beyond the schema's page_token, rate limits, or permission requirements.

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 short sentences, zero filler, with the core verb+resource front-loaded ahead of the service identifier. 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?

For a read-only list with full schema coverage and readOnlyHint set, the description is nearly complete, and listing the return fields compensates for the absent output schema. Only pagination mechanics across pages remain unaddressed.

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% – page_size, page_token and project_id are all documented in the schema, including the 'from depot_list_projects' hint for project_id. The description adds no parameter meaning beyond that, 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) plus resource (images in a project's Depot Registry) and even enumerates the returned fields (tag, digest, pushedAt, sizeBytes). No sibling tool competes for this scope, so an agent can select it unambiguously.

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?

Usage is implied by the resource name rather than stated: nothing tells the agent when to reach for this versus depot_list_builds or depot_list_projects, nor any prerequisite beyond needing a project_id. Adequate but with a clear gap in when/when-not guidance.

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