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

Annotations already declare readOnlyHint=true, so the description's 'Readable by any member' adds context about permissions and access requirements. It also explains the `stale` flag semantics ('the source model changed since the last sync in a way that moves the values'), which is valuable behavioral context beyond the schema. No contradiction with annotations.

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?

The description is compact and front-loaded: it states the core function first, then the `stale` flag detail, then access notes, then mutation alternatives. Every sentence earns its place with no redundancy.

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 one parameter and no output schema, the description covers the essential behavior, access, and related mutation tools. It does not describe the exact return format or pagination, but given the simplicity and annotations, this is a minor gap.

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%, so the schema already documents the `model_id` parameter. The description does not add further parameter-level detail beyond what the schema provides, but it does clarify that the parameter is the target model and that it may be ignored for model-scoped keys. 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?

The description clearly states the tool lists a model's external references with a `stale` flag and source health, using a specific verb ('List') and resource ('a model's external references'). It distinguishes itself from sibling tools by explicitly naming the mutation tools (layerz_external_ref / layerz_unlink_external_ref) and noting it is read-only.

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 explicitly states when to use this tool: to list external references and check staleness/source health. It also provides exclusions: 'Readable by any member, no source-model access needed' and directs mutation actions to sibling tools. This is clear guidance for an agent to select this tool over alternatives.

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