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

Annotations only declare readOnlyHint=false and destructiveHint=false; the description adds real value beyond them by disclosing the credential requirements per provider and the return values (new account_id, number of calendars discovered). It still omits failure modes, permission scope, or rate limits, so it is helpful but not exhaustive.

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 with the core purpose and the two key provider caveats front-loaded; very little wasted text. A minor structural nit is that provider specifics are appended without clear labeling, but the size is appropriate.

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 correctly summarizes the return payload (account_id and calendar count), and all five parameters are fully schema-documented. Annotations cover the mutation safety profile; the only gap is the absence of error/reauth behavior, which is minor for a straightforward connect operation.

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%, so the schema already documents every parameter, including server_url being required for Nextcloud and password meaning 'Password or App-Specific Password'. The description largely restates these, adding only the iCloud App-Specific Password hint, so the baseline of 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+resource (connect a CalDAV account) and enumerates the supported providers (iCloud, Fastmail, Nextcloud), making the tool's scope obvious. It does not explicitly contrast itself with connect_account or connect_ical_feed, so sibling differentiation is left implicit, keeping it just short of a 5.

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?

"Direct — no browser redirect needed" gives clear context for when this credential-based flow applies versus an OAuth/browser flow, and provider-specific prerequisites (App-Specific Password for iCloud, serverUrl for Nextcloud) guide correct invocation. No alternative tool is named and no explicit when-not condition is stated, so it lacks full routing guidance.

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