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

With no annotations, the description carries the full disclosure burden. It explicitly states the operation is read-only, that it snapshots the slot, and that the slot must be cast/live as a precondition. It does not cover error behavior or exact output formatting, but for a low-risk read operation this is adequate.

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 short and front-loaded, leading with the main purpose and then stating the key precondition. Every sentence earns its place and there is no redundancy with the schema.

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 purpose, primary output, read-only behavior, and the critical precondition, which is enough to invoke the tool correctly. Since there is no output schema, mentioning that it returns OCR-recognized text is important and included. It could have explicitly referenced phone-snapshot-tool as an alternative, but that is not necessary for correct invocation.

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 coverage is 100%, so the schema already documents both parameters. The description adds value by clarifying that 'slot' must be the UUID from list-phones and that display names like 'slot12' are not accepted, which is not present in the schema. Width remains self-explanatory and optional.

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 uses a specific verb and resource: 'Read the on-screen text of a farm phone' and explains it snapshots the slot to return OCR-recognized text. This clearly distinguishes it from sibling tools like phone-snapshot-tool, which would return an image rather than recognized text.

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 gives clear usage context: use this when you need OCR text from a phone screen. It also provides the important precondition that the slot must be cast/live. It does not explicitly name alternative tools or exclusion cases, but the intended use is clear enough among the sibling tools.

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