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-mutating operation. The description adds value by specifying the return payload (matching themes with DESIGN.md URL and install command), which is not implied by the annotations. This covers what an agent needs to know about behavior without contradicting the annotations.

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?

Two sentences with no filler. The first sentence establishes purpose and gives examples; the second explains the return value and the optimal usage scenario. Every clause earns its place, and the key information is front-loaded.

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?

For a read-only search tool with one required parameter and full schema coverage, the description covers all essentials: what it does, how to phrase the query, what it returns, and when to use it. The output schema is absent, but the description states the return format sufficiently. No critical information is missing for an agent to invoke it correctly.

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 schema already documents all four parameters (query, kind, mode, limit) with meanings and defaults. The description adds concrete examples ('dark developer tool', 'calm fintech dashboard') that illustrate how to phrase the query, which goes beyond the schema's 'Free text: mood, industry, colour, or use case.' This added context helps the agent construct effective queries.

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 a specific verb ('Find') and resource ('design system') and clarifies how to use it ('by describing what you are building'). It also mentions what it returns (matching themes with DESIGN.md URL and shadcn install command), which distinguishes it from siblings like list_themes and get_design_md. The phrase 'Call this first' implies a distinct role among the tools.

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 explicitly states when to use this tool: 'Call this first when the user has no design system defined.' This gives a clear condition and implies when not to use it (when a design system is already defined). It doesn't name a specific alternative tool, but the sibling list includes list_themes, which would be the natural fallback, so the guidance is sufficient though not exhaustive.

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