serial_read

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

No annotations are provided, so the description carries the full burden. It mentions the buffer cap (~64KB) and its rationale ('to protect agent context'), which is useful. However, it does not disclose whether data is cleared after reading, whether the operation blocks, or what happens when the buffer is empty. This is adequate but minimal for a read tool.

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 sentences, front-loaded with the core purpose, and a second sentence explaining the buffer cap. No wasted words; every sentence earns its place.

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 tool is simple, with full schema coverage and no output schema required. The description covers the purpose and a key safety constraint. It lacks an explicit link to serial_open as a prerequisite, but the phrase 'open serial port' implies it. Overall, sufficiently complete 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 description coverage is 100% for both parameters (encoding and maxBytes), so the schema fully documents their meaning and constraints. The description adds no parameter-specific syntax or format details; the buffer cap note is relevant context but not necessary for parameter usage. This aligns with the baseline 3.

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 and resource: 'Read buffered bytes from the open serial port.' This clearly distinguishes it from sibling tools like serial_write, serial_close, and serial_status, as it focuses on the read operation on an already-open port.

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 phrase 'open serial port' implies a prerequisite (serial_open must be called before this tool), providing clear context. However, it does not explicitly mention exclusions or alternatives among the sibling tools, so it lacks the explicit 'when not to use' guidance that would earn a 5.

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