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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely new context: every party and account is fictional, which tells the agent the payload contains no real data and is safe to embed in tests or examples. It does not describe error behavior for a bad id, but the closed enum largely removes that risk.

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, no redundancy; the return type is front-loaded and the caveat about fictional data follows. Nothing to trim.

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?

No output schema, but the description names the return format (XML of a single message), which is what an agent needs. Missing only the valid-versus-invalid distinction among sample ids, which matters because a caller expecting a usable baseline could pick a malformed sample.

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 single parameter is a closed enum, so the schema does the heavy lifting. The description reinforces that the id comes from list_samples, but it omits the most useful semantic detail: the enum mixes a handful of valid samples with dozens of deliberately malformed ones (e.g. pacs.008-unclosed-tag, camt.053-balance-mismatch). An agent must infer that from the id strings alone.

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 XML of one sample message, drawn from list_samples. An agent can immediately tell this apart from list_samples (which enumerates ids) and from validate_message (which checks a message).

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 concrete usage contexts — a starting point for authoring or for tests — and names list_samples as the source of valid ids. It stops short of stating when not to use it (e.g. against real traffic, or versus list_messages), but the intended purpose is unambiguous.

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