Design Extension

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

Annotations declare non-destructive, non-idempotent, open-world mutation, so the safety profile is covered. The description adds genuinely new behavior: 'Result files are saved to disk and their paths returned,' which tells the agent it must handle file paths rather than inline data. It omits credit/charging behavior and the interactive settings-confirmation flow, keeping it below 5.

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?

Three tight sentences with the core action front-loaded, followed by usage context and the side-effect disclosure. No filler or redundancy.

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 13-parameter mutation tool with no output schema, the description covers what the tool does, when to use it, and what it returns (file paths), with the schema supplying all parameter detail. It reasonably withholds return-value internals since no output schema exists, but says nothing about cost/credit implications or failure modes.

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 100%, so all 13 parameters are already documented in the schema, including gaps, dpi, output_dir and review_settings. The description only restates the gap range and the 'not all four 0' rule already present in the schema, adding no semantics beyond it. Baseline 3 applies.

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 and resource ('extend the design outward by a gap on each side') with the 0-10 range and the 'not all four 0' constraint, then adds a 'Best for' clause that distinguishes it from siblings like td_repeat_set or td_border_outline. An agent can identify the operation without opening the 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?

The 'Best for' sentence gives concrete usage context (growing a small swatch or centre motif outward while preserving style, palette and texture), with two worked examples. It does not explicitly name an alternative tool or a when-not-to-use condition, so it falls short of 5.

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