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

Annotations already indicate this is a non-read-only, idempotent, non-destructive write operation. The description adds little beyond saying 'replace', which is ambiguous: it could mean full replacement of all fields or partial update of provided fields. It does not clarify what happens to omitted settings or snippets, leaving a meaningful behavioral gap.

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 a single, focused sentence with no filler. It front-loads the action ('Replace') and the object ('an existing brand'). While it is terse, it is appropriately sized for the information it tries to convey, though it omits important details that would make it more useful.

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?

Given the nested settings and snippets objects and no output schema, the description is adequate but incomplete. It doesn't explain the replace semantics for partially specified objects, how to clear a field, or what the response contains. With no alternative guidance, an agent may not know whether omitted fields are reset or preserved.

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 coverage is 100%, so parameters (name, brand_id, settings, snippets) are already documented in the input schema. The description adds no additional parameter detail or usage nuance beyond the generic 'new values', so it sits at the baseline of 3 without providing extra semantic value.

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 'Replace an existing brand with new values' identifies a clear verb and resource: it modifies an existing brand. It distinguishes from creating or deleting a brand by explicitly saying 'existing', even though it does not name sibling tools. 'Replace' is slightly ambiguous relative to the tool name 'update_brand', so it loses a point.

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 use case is implied by 'existing brand' — an agent can infer this is for updating a brand that already exists rather than creating a new one. However, it does not explicitly mention alternatives like create_brand or delete_brand, nor does it state when not to use this tool. The guidance is minimal and left to inference.

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