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

Annotations declare readOnlyHint=true, openWorldHint=true, and idempotentHint=true, so the agent already knows this is a safe, repeatable, open-world read operation. The description adds that it returns a square PNG and that private/local addresses are refused, which is useful context. It does not mention potential rate limits or exact output format beyond 'square PNG', but with annotations covering the safety profile, a 4 is appropriate.

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?

A single, well-structured sentence that front-loads the core action, lists the layouts, mentions parameters, and states the return type. Every clause earns its place with no waste.

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 the tool's moderate complexity, the rich schema (80% coverage, enums, defaults, nested image object), and the presence of an output schema, the description is complete enough. The agent knows what the tool does, its key parameters, and the output format. No critical gaps.

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 80%, so the schema already documents all parameters thoroughly, including defaults, ranges, and descriptions. The description mentions 'gap and background color' and 'up to 9 photos', which aligns with the schema but doesn't add new syntax or format details. Baseline 3 is correct when the schema does the heavy lifting.

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 (arrange) and resource (photos into a collage), names the layouts, and describes the output (square PNG). It is clearly distinguishable from siblings like generate_meme or resize_image.

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 this is the tool for making collages from up to 9 photos, but gives no explicit when-to-use guidance or alternatives. Usage is implied by the tool's purpose rather than stated.

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