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

Annotations already cover destructive/openWorld/non-idempotent, but the description adds substantial context beyond them: what the default actually controls, that the MCP auto-fills the UUID, that a different workspace cannot be targeted, and the required user-settings:write scope. It stops short of saying the previous default is overwritten, which is the main thing destructiveHint=true implies.

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 tight sentences: the action and its effect first, the clearing escape hatch second, the auto-fill constraint third, with the scope requirement last. No sentence is redundant and nothing important is buried.

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 3-parameter, zero-required mutation with no output schema, the description covers effect, alternatives, constraints and auth scope. There is no return value to document and no meaningful gap an agent would need filled before calling.

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 baseline would be 3, but the description earns extra credit by clarifying semantics the schema cannot: the workspace UUID is filled automatically and cannot be aimed at another workspace from this key, so the 'workspace' parameter is effectively informational. It also explains the clear flag's effect in business terms.

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 ("Set the user's 'default workspace'") and immediately states the observable consequence (future calendar events without an explicit workspace route there). That distinguishes it cleanly from hub_get_default_workspace and the other hub_set_* tools without needing the 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?

It gives a clear when-to-use condition (routing future calendar events) and an explicit alternative path for the opposite intent ("To clear the default entirely, pass { clear: true }"). It also states a hard constraint (agents cannot target a different workspace from this key). What's missing is a pointer to hub_get_default_workspace for reading the current value or to list_workspaces for discovery.

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