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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false. The description adds genuinely non-structured behavior: a security constraint on credential handling and the credential type expected (app-specific password, CalDAV). It does not say what happens if a connection already exists or what a failure looks like, so it falls short of a 5.

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: what it connects, how to source the secret, and which alternative to use. The routing and safety constraints are front-loaded with 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 3-required-param connection tool with no output schema, the description covers purpose, input sourcing, and the sibling alternative. A minor gap is what the agent should do after connecting (e.g. select_calendar / list_calendar_connections) and whether an existing connection is replaced.

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 only 33% – calendar is documented ('provider id from list_calendars') but username and password are bare strings. The description compensates by characterizing the credential as an Apple app-specific password over CalDAV, which is the key semantic the schema lacks; username remains unstated but is self-evident.

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 and resource (connect a username/password calendar) and immediately narrows scope to Apple app-specific password / CalDAV. The sibling get_connect_links is named as the path for OAuth providers, so an agent can separate the two without reading either 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?

Explicit routing rule: use this for Apple/CalDAV credentials, use get_connect_links for Google and Outlook. It also prescribes the interaction pattern (have the user type the credentials, never reuse other secrets), so the agent knows both when to call it and how to obtain inputs.

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