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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds meaningful behavioral context beyond the schema: the default Layer is always present, and it explains the semantics of actuals_through_locked (pinned by user, source syncs will not move it). This helps the agent interpret results correctly.

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: two sentences plus a parenthetical field list. The field list is front-loaded, and the behavioral note about actuals_through_locked is valuable. Slight redundancy with the title ('List branches' vs 'List the Layer definitions') but no wasted words.

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 optional parameter and no output schema, the description covers the key semantics: what is returned, the guaranteed presence of the default Layer, and the meaning of a non-obvious field. It doesn't describe pagination or sorting, but those are minor for a list tool with annotations already covering safety.

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 model_id thoroughly, including its optionality and behavior for different key scopes. The description adds no parameter-specific meaning beyond the schema, so 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 states a specific verb ('List') and resource ('Layer definitions on a model'), and enumerates the returned fields. It distinguishes itself from sibling tools like layerz_list_models and layerz_list_transactions by specifying it lists Layers on a model, though it doesn't explicitly name a sibling alternative.

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 implies usage context: it lists Layers on a model, and the model_id parameter description clarifies when it is required vs ignored. However, it doesn't explicitly state when to use this tool over alternatives like layerz_list_models or layerz_get_model, nor does it provide exclusions or conditions.

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