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

The description is consistent with readOnlyHint=true and adds real context beyond the annotations: no account is created by the agent, the human fills in company name/email/password and accepts terms, and payment plus the money-back guarantee appear on the page. It doesn't address whether repeated calls yield the same link (the idempotentHint annotation covers that, so this is a minor gap).

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 sentences, front-loaded with what the tool returns and followed by the human hand-off constraint. The payment/guarantee sentence is supporting detail rather than filler, though it is the least essential part.

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?

There is no output schema, so the description correctly carries the return-value burden by describing the artifact as a sign-up link that already contains the selections. Combined with the annotation coverage, an agent has enough to call this correctly; only the exact return shape (URL vs. link object) is left implicit.

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 only 25% (just from_guide is documented in-schema). The description compensates partially by naming services, package and team size as the values baked into the link, which explains their effect, but it never clarifies the either/or relationship between package and services or the meaning of the team-size tiers. Enum values are largely self-describing, keeping this at a baseline-plus level.

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 concretely states what the tool produces: a pre-filled sign-up link carrying the chosen services (or a package) and team size. That is a specific resource rather than a restatement of the name 'start signup'. It does not explicitly contrast itself with ubm_quote_plan or ubm_request_plan, so sibling differentiation is only implicit.

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?

Clear hand-off framing: 'The person opens it, enters their company name, email and password... an agent never makes the account' tells the agent this is the terminal step to give to a human, not something to complete itself. It lacks an explicit 'use this instead of X when Y' routing statement against the plan/quote siblings.

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