get_principles

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the agent knows this is a safe read operation. The description adds that the tool returns 'usability heuristics, laws of UX, Gestalt principles, etc.' but does not disclose any additional behavioral traits like rate limits, authentication needs, or side effects. Since the annotations cover the safety profile, the description does not need to repeat that, but it also does not enrich behavioral understanding beyond what is already provided.

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 two sentences: the first clearly states the purpose, and the second lists the categories of principles returned. Every sentence is necessary and adds value. There is no fluff or redundancy, making it highly 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 the tool's moderate complexity with four parameters and no output schema, the description is mostly complete. It explains what categories of principles are returned and that they are matched to the context. However, it does not describe the structure of the output (e.g., whether it returns a list or a single principle, how results are ranked), which could be helpful for an agent to know how to use the results. This minor gap prevents a perfect score.

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 input schema covers 100% of parameters with descriptions and enums where applicable. The tool description does not add new meaning beyond the schema; it restates the purpose of the 'context' parameter indirectly by saying 'matched to what you're designing.' With full schema coverage, the baseline is 3, and the description does not provide additional semantic value to justify a higher score.

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: 'Get design principles relevant to a UI context.' It specificies the verb 'Get', the resource 'design principles', and the context 'relevant to a UI context.' This distinguishes it from sibling tools like 'get_pattern' or 'get_business_strategy' which focus on different types of content.

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 provides clear context on when to use the tool—when designing a UI and needing relevant principles. However, it does not explicitly state when not to use it or mention alternative tools, such as 'get_pattern' for patterns or 'get_brand_principles' for brand-specific guidance. The absence of exclusions slightly reduces the score from a perfect 5.

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