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

With no annotations, the description carries the full burden, and it does disclose the read-only nature, the 0-based part behavior, the single-part case when the result fit inline, and the not_found failure for overrun n. It does not discuss authorization prerequisites or output format, but the key behaviors are surfaced.

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?

Three sentences with no filler, and the purpose is front-loaded. The phrase 'reads back parts: 1, n: 0' is compressed to the point of mild ambiguity and could be punctuated more clearly, but the overall description is appropriately sized.

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 simple parameter set and the absence of an output schema, the description adequately covers how parts behave and what happens on overrun. It does not explain how an agent would learn the total part count or what exactly a part contains beyond the n:0 case, but those are reasonably discoverable from the not_found behavior and the tool name.

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?

The schema already describes all three parameters (100% coverage), so the baseline is 3. The description adds useful n-boundary semantics: 'n past the last part fails with not_found' and n:0 returns the full result when the result fit inline. This is helpful but not a major expansion over what the schema already documents.

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 opening sentence names a specific operation ('Read part n') and resource ('a run's result'), and immediately contrasts with host.runs.get/wait. The not_found boundary and the n:0-holds-full-result rule reinforce the semantics. Minor grammar awkwardness in the second sentence does not obscure the core purpose.

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 notes that host.runs.get/wait inline only part 0, which tells an agent when this tool is needed: to read parts beyond the inline part. It also gives the failure condition for out-of-range n. It does not spell out an explicit if-then routing rule, but the context is clear enough.

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