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

With no annotations, the description carries the full burden and does well: idempotency ('same part again is accepted and changes nothing'), a per-part size cap set by the register, a hash-validation requirement, required credential ('key'), and a rate limit (600 parts/hour). Failure/auth-error behavior is not described, 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?

Usage context is front-loaded and each clause adds a distinct constraint (size, idempotency, hash, credential, cost). The semicolon-heavy run-on and the 'Source: PD8 §10' citation are slightly noisy but largely earn their 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 3-param mutation with no annotations and no output schema, the description covers prerequisites, constraints, idempotency, and operational limits well. Return/response behavior is omitted, which is a minor gap given no output schema exists.

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 schema already documents n, part, and uploadId. The description mostly echoes these but adds the external constraint that a part may not exceed the register-declared size, a marginal value-add. Baseline 3 is appropriate.

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 verb+resource are specific: it stores one part of a sealed envelope for a chunked upload, keyed by part number. It clearly belongs to the begin_held_upload/complete_held_upload flow. It does not explicitly name those siblings, so differentiation is implied rather than stated.

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 opening ('I have opened a chunked upload and want to send its parts') establishes when to reach for this tool, and the idempotency note clarifies repeated calls are safe. No explicit alternatives or exclusions (e.g., complete_held_upload) are named, so it falls short of a 5.

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