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

Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description still adds business-level behavior beyond that: it guarantees no lead, order or payment is created and that the URL is official and public, which is exactly the side-effect reassurance an agent needs. It says nothing about auth or rate limits, but those are minor for a pure lookup.

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 short sentences with the purpose front-loaded and the disambiguating negation second. No filler, and every clause carries information the agent needs.

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 lookup with no output schema, the description usefully states what is returned (a public enquiry URL) and what is not produced (lead, order, payment). The only gap is whether the URL varies per service or how the caller should use it, which is minor at this complexity.

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% and the enum is fully enumerated with a description ('One of three small-scope entries or nine canonical service IDs'). The description adds no further meaning about how the chosen service changes the returned URL, so the schema is doing all the work and 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?

The description gives a specific verb and resource ('Get an official ACORN public free enquiry URL') and immediately rules out the most likely confusion with a sibling ('does not create a lead, order or payment', i.e. not acorn_hosted_checkout_link). It never names that sibling explicitly, so the differentiation is inferred rather than stated.

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?

Usage is implied: use this when you only need a free, non-committal enquiry entry point rather than a paid checkout or offer flow. There is no explicit 'use this when...' clause and no sibling is named as the alternative, so the agent must infer the routing rule from the negative clause.

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