purchase

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

With no annotations, the description carries the full load, but it does disclose the key behavioral trait that this is a demo and nothing is actually purchased ("only recorded"), which prevents an agent from assuming real side effects. It omits permissions, idempotency, and whether repeated calls append records.

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?

It is a single short sentence with the demo caveat front-loaded and zero wasted words. However, the terseness crosses into under-specification rather than effective conciseness.

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?

An output schema exists so return values need not be explained, but for a mutation-style tool with no annotations and 0% parameter coverage, the description leaves too much unsaid about side effects, constraints, and argument meaning to be complete.

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 0%, so both required parameters (vendor, amount_cents) are documented only by bare titles. The description adds no meaning about expected formats, currency, or units, so it does not compensate for the coverage gap, though the parameter names are largely self-explanatory.

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?

"Buy something" states a verb but the object is unspecified ("something"), so the resource is vague. The parenthetical "(demo: only recorded)" does clarify the demo nature and differentiates it from real transaction tools, which adds some value beyond the name.

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?

There is no guidance on when to use this tool versus the available siblings (send_email, publish, delete_resource, etc.), and no preconditions or exclusions. The only cue is the demo caveat, which does not help an agent decide between tools.

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