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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explicitly reveals that oversized files are refused rather than truncated, that the error includes the actual size, that maxBytes has a hard ceiling, and why this behavior matters. This is exactly the kind of non-obvious failure-mode context an agent needs and goes well beyond schema fields.

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?

The description is front-loaded with the core purpose and then logically adds root selection, size-limit behavior, and a pre-check recommendation. Each sentence provides useful information, though the 'This matters' explanatory sentence is slightly verbose and could be trimmed without losing operational clarity. Overall, it is well-organized and 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 there is no output schema, the description sufficiently explains the return value (base64 contents), the key error behavior (refusal with size reporting), and the safe fallback (use ios_file_stat). With four parameters already fully documented in the schema, there are no missing operational details that would prevent a competent agent from using this tool correctly.

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 the baseline is 3. The description adds some practical context around maxBytes and remotePath (raise the limit, narrow the path), and references ios_file_list for bundleId behavior, but these enrich rather than replace schema information. No significant semantic gap exists to compensate for.

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 states a specific verb ('Read'), a resource ('a file off an iOS device'), and the exact output format ('return its contents as base64'). It also immediately distinguishes conceptually from siblings by referencing ios_file_list for root selection and ios_file_stat for size checking, leaving no ambiguity about what this tool does.

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?

Explicit guidance is provided: when a file may be too large, either narrow the path, raise maxBytes, or 'Check size first with ios_file_stat when unsure.' The cross-reference to ios_file_list for bundleId root selection also tells the agent how to align with existing listing logic. This clearly indicates when to use this tool versus related iOS file tools.

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