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

Annotations already establish write-but-non-destructive, closed-world behavior, and the description adds genuinely new context: the operation is idempotent via a stable key, billing splits between accessed-Space operation usage and destination storage, and both Spaces must be currently accessible. It does not say what happens when an idempotency key is replayed with different parameters.

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 tight sentences, front-loaded with the action, with billing and access prerequisites following. No wasted clauses, though the billing sentence is the least actionable part for invocation.

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 no explanation, and safety is covered by annotations. But for a five-parameter cross-Space mutation with zero schema descriptions, the missing semantics for file_id/version leave the agent guessing at call construction.

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% across five required parameters, so the description carries the full burden — yet it only gestures at source/destination spaces and the idempotency key. It never explains file_id, the id pattern, or what 'version' means (the phrase 'exact retained file' hints at version pinning but is too vague to act on).

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 with scope: 'Copy an exact retained file into another authorized private Space.' This is clearly distinguishable from the file_put/file_get/file_delete siblings by the copy-into-another-Space framing, though no sibling is named explicitly.

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?

'Requires current access to both Spaces' is a real precondition, but the description never says when to choose copy over file_put (upload a new file) or file_get, nor what happens if the destination already has the file. Usage is implied rather than guided.

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