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

Annotations already establish readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuine behavioral detail: each call returns a new receipt that must be chained into the next call, and completion is signaled by a marker. However, the 'OPTIONAL: the first part already counts as delivered' sentence is ambiguous and leaves the agent unsure whether an extra call is required.

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 with the core purpose and chaining rule front-loaded and no filler. The final 'OPTIONAL' clause is cryptic rather than clarifying and slightly undercuts the otherwise clean structure.

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 no output schema, the description carries the return-value burden and does so: it says the response is the next slice plus a new receipt, and that the complete-marked part is terminal. What is missing is only a clear statement of the trigger tool and whether calling continue after the first part is ever necessary.

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% and both parameters are opaque ids whose origins are already documented in the schema ('returned by the incomplete arroway_read response', 'returned by the immediately preceding part'). The description restates the same chaining rule without adding format, expiry, or validity details beyond the schema, so the baseline 3 applies.

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 names a specific verb and resource ('Fetch the next part of a read that did not fit') and ties it to the continuation case, which distinguishes it implicitly from arroway_read, the tool that produces the initial (possibly incomplete) read. It never names arroway_read explicitly, so the sibling boundary must be inferred from 'a read that did not fit'.

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 states the precondition for use (a preceding read that did not fit, with its read_id and receipt) and gives the stopping condition ('the part marked complete is the last'). It gives no explicit when-not or naming of the producing tool, and the trailing 'OPTIONAL: the first part already counts as delivered' is unclear about whether a follow-up call is needed after part one.

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