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

Beyond the readOnly/idempotent annotations it adds real behavioral facts: the optional email is ignored, the response for a given slug is invariant to other arguments, purchases are one-time, and pricing is USD inclusive of GST for Australian buyers. These are exactly the details an agent would otherwise guess wrong about.

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 core behavior and the negative disclaimers are front-loaded and useful, but the trailing pricing sentences ('Fundamentals is free with an account... three leadership courses are US$300 once, sold together') are catalogue copy that belongs in get_course/list_courses rather than in this tool's definition.

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 one-required-parameter read-only tool with no output schema, the description covers the essential behavior, ignored input, and determinism. It is slightly ambiguous about the literal return shape — a URL string versus page content — and says nothing about how it relates to get_course.

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 both parameters are already documented, including that email is ignored. The description only reinforces that the slug maps into the returned URL path and adds no new format or validation guidance.

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+resource ('Return the public course page at https://agenticdesign.school/courses/<slug>') and explicitly disclaims what the misleading name suggests (no checkout session, no Stripe customer, no account lookup). It never names the siblings get_course or list_courses, so the boundary between 'course page URL' and 'course data' is left 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?

It supplies the selection context — 'where the buyer completes the purchase' — and a strong set of exclusions that stop an agent from using it as a checkout/session creator. There is no explicit 'use get_course for details instead' routing, so alternative selection is still inferred.

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