library_stats

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

With no annotations at all, the description carries the full burden, and it discloses almost nothing behavioral: not whether it is read-only, whether it scans the filesystem or a database, or how expensive the call is. It does imply the result is grouped counts per folder, which is the one piece of behavioral context present.

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?

One short sentence, front-loaded with the verb, and every word contributes. The compound "source/app folder" is slightly ambiguous about whether those are two distinct groupings, which keeps it from a 5.

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 annotations and no output schema, the description should say more about the return shape (key naming, whether counts are totals or nested) and whether the operation is safe/repeatable. It is minimally adequate for a zero-argument utility but leaves the agent guessing about the response structure.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. Nothing in the text contradicts or confuses the empty 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?

A specific verb ("Count") and resource ("images in the local UI library") with the grouping dimension ("per source/app folder") stated. That separates it from library_search (find images) and ui_sources (list sources), though it never names a sibling to make the distinction explicit.

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?

There is no statement of when to call this versus library_search or ui_sources, and no prerequisites or exclusions. The only implicit cue is "local UI library", which hints at scope but gives no routing guidance.

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