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

Annotations declare readOnlyHint=false and idempotentHint=true, and the description explains why: 'The first download sets the invoice date, as on the website' — a genuinely non-obvious side effect that makes the readOnlyHint=false annotation sensible. It still doesn't say what happens on repeat downloads or on failure, so it stops short of full disclosure.

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?

Two sentences, no filler, and the core behavior plus the side-effect caveat are front-loaded. Every phrase carries weight and nothing is repeated from the schema.

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 single-parameter, no-output-schema tool whose annotations cover safety and idempotency, the description is nearly sufficient: it says what it produces and flags the state-changing first download. It could still note whether the PDF is returned inline or as a link/URL.

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% and already explains how to build orderId from get_renewal_quote/create_renewal_order or the LEI GUID. The description only restates the same dual nature ('registrations or renewals') without adding syntax, format, or validation detail, so baseline 3 applies.

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 ('Returns the PDF invoice') plus the scope ('for one of the user's LEI registrations or renewals'), which is far more useful than the tautological title 'Download invoice'. It does not, however, distinguish itself from the sibling get_invoice or list_my_invoices, leaving the agent to infer the split.

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?

Gives a concrete triggering context ('e.g. to pay a renewal ordered with payment by invoice'), which tells the agent when this tool is the right call. It stops short of explicit exclusions such as when to prefer get_invoice over this one.

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