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

With no annotations, the description carries the full burden and does reasonably well: it discloses access requirements (no login, free), the mechanism (HTTP scrape rather than a browser session), and the semantic payload returned. It does not mention rate limits, caching, failure modes, or cost ceilings, so it is not exhaustive, but the auth/mechanism profile is genuinely useful.

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?

Front-loaded with the verb+resource, then the return payload, then exclusions, then the endpoint. Three sentences, all earning their place, though 'TypeSafe Jev typed decisions' is jargon that adds little for an agent and could be trimmed.

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 exists, and the description compensates by enumerating the returned fields (use-case mention, price clarity, agent-friendly description, cart-blocker suspicion, readiness score). Combined with the auth and mechanism disclosure, an agent has enough to invoke correctly; only ambiguity about which of the three parameters to supply keeps it from a 5.

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 url, host, and slug are already documented in the schema; baseline is 3. The description only adds a sample endpoint fragment ('GET /api/agent-facts?host=') that hints at the host parameter, with no guidance on precedence between url/host/slug.

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 (Read) and resource (ARC agent facts) scoped to a store or product, and explicitly names what it is NOT: a browser session, a third-party agent product, or ARC's browser cart tests (shoppers A–E). An agent can distinguish it from checkout-oriented siblings like can_agent_checkout or precheck without opening a schema.

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 clear usage context ('free', 'no login', HTTP scrape) and an explicit exclusion ('Not a browser session... browser cart tests are separate'), which steers agents away from the wrong tool class. It stops short of naming the specific sibling to call for browser cart tests, so the routing guidance is implied rather than complete.

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