Send simultaneous Android keys

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

Annotations already declare this as a non-destructive but non-idempotent write operation, so the safety profile is covered. The description adds useful behavior: keys must be device-supported, ordering is significant, and durationMs governs the chord hold, but it omits auth requirements, device/session preconditions, and rate limits.

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?

One front-loaded sentence with no filler; the essential verb and resource lead the sentence. It is clean but extremely terse for a 5-parameter tool, leaving no room for structural grouping of constraints.

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?

With an output schema present, return values need not be explained, and annotations cover safety. However, for a required 3-parameter input tool with only 40% schema coverage, the description omits key string format, source semantics, multi-device serial rules, and when to prefer this over sibling input tools, leaving meaningful gaps.

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 40%, so the description must compensate. It adds meaning for the keys array ('explicit ordering') and durationMs ('chord duration'), but gives no explanation of the source enum values or the key-string format expected in the array.

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 (inject) and resource (key combination) plus scope modifiers (ordering, chord duration). The word 'combination' conceptually separates it from mobile_input_key (single) and mobile_input_key_sequence (sequential), though no sibling is named explicitly.

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?

There is no when-to-use guidance, no conditions for choosing this tool over mobile_input_key, mobile_input_key_sequence, or mobile_input_text, and no prerequisites or exclusions. Usage is only weakly implied by the word 'combination'.

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