Pull a file from the device. Returns base64-encoded content. Default size cap 5242880 bytes (5MB); pass maxSizeBytes to override up to 20971520 bytes (20MB). Refuses directories and oversized files before transferring. Returns { ok, remotePath, sizeBytes, content (base64) }.
| Name | Required | Description | Default |
|---|---|---|---|
| udid | Yes | Device serial number (UDID) | |
| remotePath | Yes | Absolute path of the file to pull | |
| maxSizeBytes | No | Override the default 5MB cap; max 20MB. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral disclosure burden. It covers the return format, default and maximum size caps, the override parameter, and refusal behavior before transfer. This is solid transparency for a read-style pull operation, though it does not discuss error cases or permission requirements.
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 focused sentences with no filler. The core action and return type are front-loaded, followed by the size cap details and refusal behavior. Every sentence contributes essential operational information.
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 is complete for a tool of this complexity. It covers the return value shape, parameter behavior, limits, and edge cases such as directories and oversized files. Without an output schema, it appropriately documents the response structure inline.
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 meaningful parameter semantics beyond the schema by explaining the default 5MB cap, the maxSizeBytes override up to 20MB, and that oversized files are refused before transfer. This elevates it above baseline.
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 the specific operation ('Pull a file from the device'), the resource (a remote file), and the output format (base64 content). This naturally distinguishes it from related siblings like device_file_push, device_file_list, and device_file_stat.
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 clear context for when to use the tool: to retrieve a file's content from a device. It also communicates size limits and refusal behavior for directories and oversized files, giving an agent enough to decide appropriate usage. It does not explicitly name alternative tools or exclusion scenarios, but the context is strong.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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