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

Beyond the annotations, the description discloses critical side effects: setting actuals_through pins the cutover and sets actuals_through_locked: true, while null resets to auto and clears the pin. It also adds the auth restriction ('Not available for read-only API keys'). This is rich behavioral context that annotations alone do not provide, and it does not contradict the idempotentHint or destructiveHint 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 dense but well-structured: it front-loads the core action and fields, then explains the nuanced actuals_through behavior, then the auth limitation. Every sentence contributes useful information, though the pinning explanation is slightly long and could be tightened.

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 patch operation with a nested object and no output schema, the description covers purpose, editable fields, default-Layer constraints, side effects, and auth. Gaps include no mention of dataset_id semantics, model_id handling beyond the schema, or return value, but the schema already documents model_id and summary well, so the description is mostly complete for an agent to call it correctly.

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?

With only 50% schema description coverage, the description compensates by enumerating all patch fields and explaining actuals_through semantics in detail, including the pin/reset behavior and the default-Layer restriction. However, it does not explain dataset_id, priority, source_hint, or file_name beyond their names, so the compensation is strong but incomplete.

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 opens with a specific verb and resource: 'Patch an existing Layer' followed by the exact editable fields. It is clear about what the tool does, but it does not differentiate itself from the sibling layerz_patch, and the title says 'Update branch' while the body refers to a 'Layer,' which creates mild ambiguity.

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 gives useful usage constraints: the default Layer only accepts a subset of fields, and read-only API keys cannot use this tool. However, it never states when to use this tool instead of a sibling like layerz_patch or layerz_import_branch, so the usage guidance is implied rather than explicit.

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