Rebuild the original from parts

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

Beyond the annotations, the description discloses the verification method (per-file size + SHA-256), the failure contract (names missing_parts / missing_names / corrupt_parts), the AgentParcel-apps.zip exclusion, and that output never overwrites. This is exactly the mutation-adjacent behavior an agent needs and is consistent with destructiveHint=false.

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 core action, then input forms, then failure semantics, then the extract caveat — every sentence carries information. It is dense and terse to the point of reading like notes, but there is no filler.

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?

With an output schema present, return-value detail is not required, and the description covers inputs, verification, failure naming, and non-overwrite behavior. The one soft spot is what happens on a collision ('never overwrites') — whether that is an error or a renamed output is left implicit.

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 100%, so the baseline is 3; the description adds meaning by clarifying that extract applies only to rebuilt zips and not to byte-split files, and that password is unnecessary for zip/plain sets. It still doesn't elaborate on output_dir behavior beyond what the schema states.

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 (rebuild the original from AgentParcel parts) and immediately disambiguates the two supported input families: zip part sets and byte-split sets. It is clearly the inverse of the split_* siblings and is distinguishable from verify (which checks without reconstructing).

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 spells out the three acceptable ways to supply parts (folder, any single part, explicit list) and scopes extract to zip sets only, explicitly excluding byte-split files. It doesn't explicitly say when to prefer it over siblings like verify or regenerate_parts, but the context of use is unambiguous.

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