read_phone

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

With no annotations, the description carries the full burden, and it does disclose the critical destructive trait: 'Discards any unapplied draft.' That is the single most important caveat and it is stated plainly. However, it omits other behavioral context a caller needs, such as what happens if no iPhone is connected or whether device trust/permission is required, and it does not characterize the returned draft.

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 short sentences, zero filler, with the read operation front-loaded and the destructive side effect immediately following it. Every sentence earns its place by conveying a distinct fact the agent needs before calling.

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?

For a zero-parameter tool with an output schema, the description covers the action, the source, and the destructive consequence, which is essentially the full decision surface. The only meaningful gap is the absence of any precondition about device connectivity or authorization.

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?

The tool takes zero parameters, so there is no parameter semantics for the description to add; the baseline for a parameterless tool applies. Nothing in the description misrepresents the argument surface.

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 the Home Screen from the connected iPhone') plus a secondary effect ('start a fresh draft from it'), which clearly distinguishes it as a device-to-draft ingest step rather than a mutation like apply or move. It stops short of naming sibling alternatives such as reset_draft or restore, so it is clear but not fully differentiated.

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?

Usage is only implied: the agent can infer this is the entry point that seeds a working draft from the live phone state. There is no explicit when-to-use or when-not-to-use guidance, and no statement about how it relates to reset_draft, restore, or diff, so the agent must infer call ordering.

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