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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the agent knows this is a safe, non-destructive read/query operation. The description adds minimal behavioral context beyond the example; it doesn't mention output format details or any side effects, but that is fine given the read-only nature. Without annotations, it would score lower, but with them, a 3 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?

The description is concise, with two clear sentences: the first states the purpose, the second provides a concrete example. There is no unnecessary redundancy. It is appropriately sized and front-loaded with the core action. The example slightly increases length but adds significant clarity, so a 4 is justified.

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 (two parameters, one required, with clear schema and annotations), the description is adequate but not highly informative. The output schema is missing, so the description could have explained what the composite output looks like or mentioned that the format parameter controls output. However, the tool is simple enough that a 3 is reasonable; it covers the main purpose but lacks some behavioral detail.

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 the parameters (compositions, format) are fully described in the JSON schema. The description adds the crucial concept of 'mixing tokens' and gives an example, which helps understand the 'compositions' parameter. However, since the schema already explains the structure and enums, the description's extra value is moderate. Baseline 3 is appropriate.

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 purpose: 'Mix tokens from different design systems to create a custom composite.' This distinguishes it from related tools like generate_design_system or get_design_system, which are about creating or retrieving systems, not composing across systems. A concrete example is provided, enhancing clarity.

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 gives a concrete example of when to use it, but does not explicitly state when not to use it or mention alternatives. However, the sibling tool names (e.g., generate_design_system, get_design_system) offer some implicit context, and the example implies composition use cases. There is no explicit guidance on where this fits in a workflow, so it falls short of a 4.

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