measure_text

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

With no annotations, the description carries the behavioral disclosure burden. It clearly states that the operation does not mutate a sprite, which is useful. But it does not disclose what is returned, how font resolution works, or whether an invalid font causes an error.

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 short sentence with no filler. The essential identifying behavior is front-loaded, and every word contributes meaning.

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?

While the tool appears simple, there is no output schema and no description of the return value, so an agent cannot predict what 'measure' yields. Parameter semantics and valid font usage are also left undocumented, making this incomplete for reliable 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 0%, so the description needed to explain the six parameters, but it only says 'text run'. It provides no meaning for font, size, bold, letter_spacing, or antialias, and notably leaves the integer type of 'bold' and the scaling semantics of 'size' unexplained.

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?

Uses a specific verb and resource: 'Measure a text run'. The qualifier 'without changing a sprite' clearly distinguishes it from rendering tools like draw_text. The tool's purpose is immediately unambiguous.

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 implies a read-only measurement use case and signals that it should not be used when the goal is to draw or modify a sprite. However, it does not explicitly name alternatives such as draw_text or state when to prefer this tool over related text or layout operations.

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