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

Annotations declare destructiveHint=true, so the description doesn't need to restate that. It adds behavioral context by noting recursive directory copying and multi-path support, which the schema doesn't explicitly cover. However, it doesn't warn about the default overwrite=true behavior, though the schema does document the 'overwrite' parameter. No contradiction with annotations.

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 sentences, no fluff, with the core usage condition front-loaded. Every word 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?

Given the tool's moderate complexity (multi-path, overwrite, device requirement), the description covers the core use case and differentiation. Device and overwrite details are fully in the schema, and output schema exists. It doesn't mention potential side effects of overwriting, but that's covered by the destructive annotation and parameter description. Sufficient for correct selection and invocation.

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 all parameters are already documented. The description adds context that 'paths' is meant for multiple entries and directories, but doesn't add detail on 'device' or 'overwrite' beyond what's in the schema. It provides marginal added value.

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?

The description clearly states the tool copies directories recursively or multiple paths in one request, and explicitly contrasts it with copy_file for a single regular file. This distinguishes it from siblings and gives a specific verb and resource.

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?

It explicitly states when to use this tool (directory recursive copy or two+ paths) and when not to (exactly one regular file) by naming the alternative copy_file. This provides direct routing guidance.

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