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 warns that oversized files are refused rather than truncated, reports the actual size in errors, and explains the rationale (silently clipped data is indistinguishable from corrupt). It also discloses the hard ceiling on maxBytes, which is critical context for avoiding data loss.

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 three sentences long, front-loaded with the core purpose, and every sentence earns its place. The warning is concise but impactful, and the final sentence provides a practical fallback without padding.

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?

The description covers the essential behavioral details and parameter guidance, but since there is no output schema, it does not fully specify the response structure (e.g., whether the base64 is wrapped in a JSON object with additional fields). This leaves minor ambiguity about the exact return format, though the core content is stated clearly.

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 value by explaining the interplay between maxBytes and file size (raising it or narrowing the path to avoid refusal) and cross-referencing bundleId selection with ios_file_list, providing context beyond the schema's field descriptions.

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 clearly states 'Read a file off an iOS device and return its contents as base64,' which identifies the verb, resource, and output format. It distinguishes itself from siblings like ios_file_list (list files), ios_file_stat (metadata), and ios_file_push (write) by specifying the read-and-return action.

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 description provides actionable guidance by recommending 'Check size first with ios_file_stat when unsure' and explaining how to handle oversized files (narrow the path or raise maxBytes). It also references ios_file_list for bundleId selection conventions, giving context for when to use this tool versus others.

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