fill_region

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

No annotations provided, so description carries full burden. It mentions two modes but does not disclose that the operation modifies the canvas irreversibly, nor does it explain behavior when match conditions are all false. Additional behavioral details would be beneficial.

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?

Description is two sentences, front-loaded with action and variants. Every word earns its place; no 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?

With 9 parameters, no output schema, and many sibling tools, the description is too brief. It omits return value, error cases, prerequisites, and does not help differentiate from similar tools like batch_recolor or batch_replace_char.

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 100% so parameters are individually described. The description adds only a high-level explanation of 'contiguous' vs 'global', but doesn't clarify interactions between matchChar, matchColor, matchBgColor, or default behavior when all are false. Minimal value added beyond schema.

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?

The description states 'Fill a region with a character and colors' which is a clear verb+resource. It distinguishes from siblings by specifying two modes: contiguous and global, but could be more explicit about the starting coordinate involvement.

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 explains when to use contiguous vs global (based on connectivity), but does not compare to alternatives like batch_recolor or select_by_color. No explicit 'when not to use' guidance.

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