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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so safe-read semantics are covered. The description adds genuinely useful behavior: the callback is handled by the web app not MCP, the mailbox will not appear in email_account_list until the user finishes, and the plan gate. However for a closed-world read-only URL builder, these additions are contextual rather than critical gaps, so a 3 is fair.

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?

Front-loaded with the core action, then handoff semantics, sibling preference, exclusion, and plan requirement. Every sentence supplies distinct information 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?

No output schema exists, but the description explains that returning the URL is the whole job and that the callback occurs elsewhere. For a 2-parameter read-only builder this is complete enough to invoke correctly.

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% for both parameters, including `state` and the `provider` enum. The description adds only implicit mapping (Google/Microsoft) which the enum already states, and says nothing new about `state`. 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+resource ("Build the Google or Microsoft consent URL for connecting a mailbox") and immediately differentiates from the sibling email_account_add_imap. An agent can identify the tool and its scope without opening 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?

Explicitly covers when to use (Google/Microsoft preference over IMAP, no password, survives 2FA), when not to (no LinkedIn equivalent), the handoff flow (give URL to user for browser), and prerequisites (Pro or Agency plan). This is the full when/when-not/alternatives set.

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