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

Annotations already declare it non-readonly, idempotent, and non-destructive; the description adds substantial extra context on top: the side effect ('The previous default stops being the default'), the return value ('Returns the updated role'), and a specific failure mode ('Fails with ROLE_NOT_FOUND, listing the app's role keys'). This is rich disclosure beyond structured data.

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 core purpose, argument, and side effect are front-loaded effectively, but the tail drifts into general authorization advice (hard-coded role checks, privilege-key matching semantics, integration-guide pointers) that does not directly help an agent invoke set_default_role. For a simple two-parameter mutation the description is padded.

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?

With no output schema, the description covers the return value, the error case, the replaced-default side effect, and the prerequisite reads, which is nearly everything needed to call it. It omits any statement of required permissions/caller authority, which is the only notable gap.

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%, and the schema already documents both 'app' and 'key' with the exact 'Role KEY from list_roles, e.g. MEMBER' wording. The description repeats that phrasing rather than adding syntax or format detail, so the schema does the heavy lifting and the baseline of 3 applies.

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?

States a precise verb and resource ('Make an existing role the default') and immediately defines the concept ('the role a person gets when they are added to a workspace without a role named'). An agent can distinguish this from siblings like create_role, update_role, and get_role without opening a schema.

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?

Gives clear context: read roles with list_roles first, ask the developer rather than picking a default, and call get_integration_guide before writing consuming code. It names prerequisite/related tools, but does not explicitly contrast this tool against the closely-related update_role, so the routing is slightly incomplete.

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