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

Annotations already declare readOnlyHint=false, destructiveHint=true and openWorldHint=false, so the mutation profile is covered. The description adds what actually changes — the implicit account used by M365/Teams tools — but says nothing about persistence (global vs per-session), whether it can be reverted by calling the same tool with another account, or side effects on in-flight calls, which is notable given destructiveHint=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?

Two short sentences, front-loaded with the action and its effect, followed by the accepted identifier forms. No 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 one-parameter configuration tool with full schema coverage, annotations, and an output schema, the description supplies the essential effect and value discovery path. The remaining gap is persistence/reversibility semantics, which the output schema cannot convey.

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 parameter description already lists 'email (upn), id, or display name', which the description repeats verbatim in substance. The only added value is the pointer to list_m365_accounts as the way to obtain valid identifiers, so 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?

The description names a specific action (setting a default) on a specific resource (the connected Microsoft 365 account) and states the downstream effect: it determines which account the M365 and Teams tools use when no `account` is supplied. That is clearly distinguishable from connect_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?

It explains the condition under which the default matters ('when no `account` is given') and routes discovery to list_m365_accounts. It does not state when-not to use it (e.g. if only one account is connected, or per-call `account` overrides it), but the usage context is clear.

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