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

The readOnlyHint/openWorldHint annotations already cover the safety profile, so the description's job is to add search-specific behavior. It does disclose the indexed fields and result ordering ("returns the best matches first"), which is genuinely useful, but says nothing about match scoring, empty-result behavior, or how filtering interacts with ranking.

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?

Three short sentences ordered as purpose, query style, then call-to-action. The example queries are the highest-value content and are front-loaded, and nothing is redundant with the schema or annotations.

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?

With no output schema, the description at least signals ranking order and the fact that matches are returned, which is the main thing an agent needs to know before calling. It could say more about result shape or what an empty match implies, but for a 5-param search tool this is close to complete.

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 100%, so baseline is 3, but the description goes beyond the schema's "What the UI has to do" by supplying three concrete natural-language query examples that teach the intended phrasing style. The other four params (tier, type, category, limit) are left to the schema.

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?

"Find PixilUI items for a UI job" pairs a specific verb with a specific resource, and "Searches titles, descriptions, when-to-use notes and tags" defines the search surface precisely. It never names a sibling (get_item, list_items) to draw the boundary explicitly, so search-vs-browse-vs-fetch has to be inferred from vocabulary rather than stated.

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?

"Call this before writing any UI by hand" gives an unambiguous trigger for reaching for this tool, and the three quoted example queries show how to phrase a request. There is no when-not guidance and no explicit routing to get_item or list_items once a match is known, which keeps it below a 5.

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