character_expression

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

Annotations declare readOnlyHint=false and idempotentHint=false, so the agent knows this mutates display state; the description adds the key disclosure that it 'replaces screen content,' telling the agent existing display content is overwritten even though destructiveHint is false. It stops short of saying how long the expression persists or what clears it.

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 short sentences, zero waste, with the core action and the display-replacement consequence front-loaded. Nothing redundant against the name.

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?

A no-output-schema mutation tool with annotations already covering safety; the description covers purpose and the main side effect, but omits the undocumented 'intensity' parameter's meaning and any note on persistence. Adequate but with a clear gap for an agent composing calls.

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 0%, so the description must carry parameter meaning. It names emotion and activity (whose enum values are already self-documenting in the schema) but says nothing about 'intensity' — no range, units, or effect — leaving one of three parameters undocumented anywhere.

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 (show) and resource (the configured character) plus the two expressive dimensions (emotion, activity), and clarifies 'without speaking,' which separates it from character_speak. It does not name siblings explicitly, but the implicit contrast is readable.

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 'without speaking' implies when to prefer this over speaking tools, but the description never names character_speak or speak as alternatives, nor states any exclusions or prerequisites. Usage is inferable rather than instructed.

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