measure_between

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

With no annotations, the description carries the behavioral burden and reveals important side effects: it registers a scope measurement, may populate the results panel, and enables disabled sources. It also discloses a precondition and an invalid value sentinel, though it does not describe the exact return shape or error behavior.

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?

Four short sentences deliver purpose/units, item semantics, side effects, and operational caveats, with every sentence adding distinct value. The core action is front-loaded.

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 small three-parameter tool with no annotations or output schema, the description covers purpose, units, parameter interpretation, side effects, a device-specific precondition, and an invalid-result sentinel. An agent has enough information to select item values and know what to expect.

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 schema already labels source1 and source2 (67% coverage); the description adds essential meaning to the cryptic item enum by explaining edge-letter order and DS1000Z-to-DHO mapping. This goes beyond the schema, though it leaves R/F expansion to the agent's domain knowledge.

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 opening phrase 'Read delay (seconds) or phase (degrees)' names a specific verb, resource, and unit, making the tool's core function unmistakable. This is clearly distinct from generic siblings like measure or get_scope_state.

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 context: this is for delay/phase measurements between two sources. It also supplies operational prerequisites and caveats (live acquisition on DHO, invalid sentinel 9.9E37), though it does not explicitly route the agent away from the sibling measure tool.

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