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

Discloses behavior well beyond the annotations: oversized files are REFUSED rather than truncated, the error reports the actual size, and there is a hard ceiling. This is exactly the kind of non-obvious behavior an agent needs. It stops short of stating session/auth prerequisites or whether the pulled content is cached, and the annotations' readOnlyHint=false is not explained by the description, but no direct contradiction exists since the description never asserts the absence of side effects.

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?

Five tight sentences, front-loaded with the core action and followed by scope, failure mode, and a pre-check. The 'This matters' sentence earns its place by motivating the refusal semantics, and nothing is redundant.

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 correctly notes the return is base64, and it covers the significant failure mode, the sibling to check first, and container selection. Only minor gaps remain (no mention of required session/auth state or call cost for large files).

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 four parameters are already documented (including 'default 5 MB, capped at 25 MB'), setting the baseline at 3. The description's 'raise maxBytes / narrow the path' adds workflow context but no syntax or semantics the schema lacks.

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 ('Read a file off an iOS device') plus the return representation ('base64'). It also differentiates itself from the two adjacent siblings it names, ios_file_list (root selection) and ios_file_stat (size pre-check).

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?

Gives explicit when-to-use guidance: 'Check size first with ios_file_stat when unsure', and prescribes the recovery path when the read is refused ('narrow the path or raise maxBytes'). Alternatives are named by name, not left to inference.

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