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

Annotations only declare readOnlyHint=true, so the description carries real weight and delivers: free of charge, rate limited per address, no values returned, newest-first ordering, and an authorization rule (anyone with the box id). It omits pagination/result caps, which matters for a list operation on a keyspace, keeping it from a 5.

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?

One compact sentence group that front-loads the resource and return shape, then cost, then access rule. Every clause (ordering, no values, cost, auth) earns its place.

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 single-parameter read-only list with no output schema, the description covers return fields, ordering, cost, and access. The one meaningful gap is behavior when a box holds many keys — no mention of limits or pagination.

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 0% for the single 'box' parameter, so the description must compensate; it does partially by tying 'box' to a box id that acts as the access credential. It adds no format, source, or validation guidance for that id, leaving the compensation incomplete.

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?

Specific verb ('List') plus resource ('the keys in a box') and an explicit statement of what is returned (seq, size, expiry) and what is not (values). The 'without values' clause implicitly separates it from the sibling 'get', but no sibling is named outright, so it stops just short of a 5.

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 'without values' phrasing implies you follow up with 'get' for values, and 'Anyone holding the box id can do this' establishes the access precondition. There is no explicit when-to-use/when-not statement or named alternative, so usage is only implied.

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