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

Annotations already indicate it's not read-only, not destructive, and idempotent. The description adds substantial behavioral detail beyond that: it persists for the API key until changed, works across all surfaces including hosted connectors, and verifies real membership for shared workspaces before pinning. No contradiction with annotations; the description enriches the safety and side-effect profile.

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 thorough but not wasteful. It front-loads the primary purpose, then provides necessary detail on shared brands and persistence. The sentences are structured logically, covering scope, usage, and behavior without redundancy. It's slightly long but every sentence adds value, making it appropriately concise for the complexity.

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 there is no output schema, the description does not explicitly state what the tool returns, but it covers the core aspects: what it does, how to use it, accepted parameter formats, persistence behavior, and shared-workspace handling. It does not mention error conditions or explicit success confirmation, but for a simple pinning operation, the description is reasonably complete.

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?

Although the schema covers the parameter at 100%, the description adds significant meaning beyond it. It explains the three accepted formats (brand id, exact name from list_brands, or profile id for shared workspaces) and references list_brands as the source of valid values. This guidance is crucial for correct invocation and goes well beyond the schema's simple description.

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's purpose: to 'Pin which brand this connection acts on' for multi-brand accounts. It uses a specific verb ('Pin') and resource ('brand'), and distinguishes it from siblings like get_brand, create_brand, and update_brand by focusing on selection/activation rather than CRUD operations. The mention of multi-brand accounts adds context, and the clarification about shared workspaces further differentiates its scope.

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 explains when to use the tool—when you need to set the active brand for the connection—and mentions that 'list_brands' provides the valid id/name values. It also implies the tool is the one to use for shared workspaces, verifying membership. However, it does not explicitly state alternatives or provide exclusions, but the context is implied strongly enough for an agent to decide appropriately.

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