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

Annotations declare readOnlyHint=false and destructiveHint=false, so the mutation/non-destructive profile is already covered. The description adds genuinely useful context beyond that: the setting is scoped locally ('Only runs on the computer itself, not through the cloud connector'), which tells the agent this change does not propagate to the cloud connector. It doesn't state reversibility or auth needs, but that is a minor gap given the annotations.

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 short sentences, front-loaded with the action and effect, then the identifier hint and the local-scope caveat. Every sentence earns its place; no redundancy or filler.

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 single-param mutation tool with an output schema, the description covers what it does, the identifier forms, the effect on other tools, and the local-only scope. Nothing essential is missing; only deeper operational details (reversibility, auth) are absent, which is acceptable given the annotations and output schema.

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% and the single `account` param is fully described in the schema, so the schema does the heavy lifting. The description largely mirrors the schema's 'email (upn), id, or display name' wording, adding only the pointer to list_m365_accounts as a source of valid values. Baseline 3 is appropriate.

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 specific verb (set/choose default) and resource (connected Microsoft 365 account) and explains the downstream effect: the M365 and Teams tools will use this account when no `account` is given. This cleanly distinguishes it from siblings like connect_m365_account, disconnect_m365_account, and list_m365_accounts.

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?

Explains the triggering condition ('when no `account` is given') and points to list_m365_accounts for obtaining valid identifiers, giving the agent clear context for use. It stops short of stating explicit exclusions or prerequisites (e.g., that an account must already be connected), so it is clear context without full when-not guidance.

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