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

With no annotations supplied, the description carries the full burden and does disclose a real behavioral contract: it returns do_not_answer when a fact is drifted or unverified and never guesses. That is genuinely useful, though it omits what happens on an unknown fact_id or what the refusal payload looks like.

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 zero filler, and the most important behavior (refusal rather than guessing) is front-loaded. Nothing needs trimming.

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-parameter lookup with no annotations and no output schema, the description covers purpose and refusal semantics but leaves the agent without id discovery guidance or any sense of the returned fact's shape. It is adequate but leaves clear gaps an agent would hit on first use.

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?

The single parameter fact_id has 0% schema description coverage, so the description must compensate and does not — it never says what a fact_id looks like or that ids come from railcomp_list_facts. The only hint is the implicit 'one fact' framing.

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 ('Get one verified fact') and scopes it to the railcomp pack, and the word 'one' implicitly separates it from railcomp_list_facts. It does not explicitly name the sibling list/changes tools, so 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?

The description signals it is a single-fact lookup by id and notes refusal conditions, which implies when it is applicable. It never says when to use railcomp_list_facts or railcomp_changes instead, and gives no prerequisites for obtaining a valid fact_id.

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