Record an Android display

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

Annotations already declare readOnly=false, idempotent=false, openWorld=true, destructive=false. The description adds non-obvious behavior beyond these: the call is BLOCKING and the duration is bounded (matching the 180s schema max), which is important context for planning. It omits where the resulting artifact lands, though an output schema exists.

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 tight sentences with zero filler. The core operation and scope are front-loaded, and the sibling routing follows immediately.

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?

Annotations cover the safety profile and an output schema covers return values, so the description only needs behavioral nuance—which it supplies (blocking, bounded, single display target). Complete enough to invoke correctly; only artifact/destination details are unaddressed, and those are arguably covered by the output schema.

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 67% and the two complex params (serial, displayId) already carry rich inline descriptions, including the logical-vs-physical display distinction. The description adds little parameter-level detail and leaves durationSeconds semantics to the schema bounds/default. Baseline 3 given the schema does the heavy lifting.

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 (record) and resource (one physical-backed display) with clear scope (bounded duration). It also names the sibling family it competes with (mobile_record_start/mark/stop), so an agent can distinguish it without opening either schema.

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?

Explicitly routes the agent: 'Prefer mobile_record_start/mark/stop when input must be interleaved.' This gives a concrete condition selecting the alternative. It stops short of stating when NOT to record at all, so it's clear but not exhaustive.

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