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

The description adds meaningful behavioral detail beyond the annotations: it discloses upsert semantics ('only the fields you pass are changed') and the non-obvious side effect that setting is_default true removes the default flag from other profiles. This is exactly the kind of context an agent needs and does not contradict readOnlyHint=false or idempotentHint=true.

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?

Three dense sentences with no filler: purpose, patch semantics, and the default-flag caveat. Every sentence earns its place and the most important behavioral constraint is front-loaded.

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 rich schema, annotations, and the description's explicit coverage of create-vs-update, partial patching, content-plan linking, and default uniqueness, the agent has what it needs to invoke the tool correctly. The main omission is the return value, and with no output schema that is a minor gap rather than a correctness risk.

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 descriptions already cover all 10 parameters at 100% coverage. The description adds cross-cutting parameter semantics beyond the schema: name is the upsert key, all other fields are optional patch fields, and is_default and content_plan_id carry behavioral side effects that their individual schema entries do not fully convey.

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 what the tool does: it saves a client's brand guidelines and creates or patches a brand profile by name. This distinguishes it from sibling read tools like get_brand_profile and list_brand_profiles without requiring the agent to inspect schemas.

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 clear context for when to use it: to make future copy sound like a client's brand and optionally attach the profile to a content plan. It does not explicitly name alternatives or state when not to use it, but the purpose is specific enough that routing is unambiguous.

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