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

Annotations only declare readOnlyHint=false, openWorldHint=true, idempotentHint=false and destructiveHint=false; the description adds the real behavior: an email is sent, the account is created or logged in on link open, no password exists, and the flow is outbound to an external person. It also discloses a genuine eligibility restriction — an estate agent's email with a PropertyList CRM login cannot be used — which the annotations cannot convey.

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?

The action and its mechanism are front-loaded in the first two sentences, and the operational rules (no password, check email, agent-email restriction) follow in priority order. The benefit sentence about saved homes and enquiries is slightly promotional but does help the agent explain the value to the user, so little is wasted.

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 three-parameter, open-world creation tool with an output schema available, the description covers the mechanism, the safety rule, the eligibility restriction, and what to tell the user. Nothing an agent needs in order to call it correctly and explain the outcome is missing.

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 baseline is 3; the description earns an extra point by attaching a real constraint to the email parameter (agent emails with CRM logins are rejected) and by framing language as affecting both the email and the account. It does not add syntax, format, or validation detail beyond what the schema already states.

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 gives a concrete verb and resource: "Create a free PropertyList buyer account for a person, or let them log in to the one they have, by email." It also explains the mechanism (emailed magic link), so the agent knows exactly what the call produces. It stops short of naming a sibling such as create_contact to disambiguate contact creation from buyer-account creation.

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 gives clear use conditions (a buyer needs an account, or an existing buyer needs to log in) plus follow-up instructions ("Tell the person to check their email") and an explicit prohibition ("Never ask for or make up a password"). What's missing is guidance on when to prefer an alternative such as create_contact when the person is not a buyer.

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