label_regions

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

No annotations are provided, so the description must carry the full burden. It states 'Quickly label' but does not disclose whether the operation modifies the image, requires prior image loading, or what the return value is. For a tool that likely alters an image, this lack of side-effect disclosure is a significant gap.

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?

The description is concise, with a clear opening sentence and a helpful example. It avoids unnecessary fluff and front-loads the purpose. The example is well-formatted and directly illustrates the 'regions' parameter, making it efficient for an agent to parse.

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?

Given that an output schema exists and the input schema covers all parameters, the description is adequate but not fully complete. It doesn't mention any prerequisites like requiring an image to be loaded (sibling tools include load_image), nor does it explain the output format beyond what the schema likely covers. For a tool that modifies an image, this is a notable omission.

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?

The schema already provides 100% coverage with descriptions for all four parameters, including an example for 'regions'. The description adds a slightly different example, but this doesn't go beyond the schema's explanation. With high schema coverage, a baseline of 3 is appropriate; the description adds marginal value but doesn't compensate for any missing details.

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 clearly states the tool's function: 'Quickly label multiple regions of an image.' It specifies the verb (label), resource (regions of an image), and the 'multiple' aspect distinguishes it from single-region annotation tools like add_box or add_text. However, it doesn't explicitly differentiate from sibling tools like annotate or batch_annotate, so it's not a perfect 5.

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 'Quickly label multiple regions' implies batch usage, which is a clear context for when to use it over single-label tools. It also provides an example that clarifies the expected input format. However, it doesn't explicitly state when not to use it or name alternative tools, so it misses some guidance.

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