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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds useful behavioral context beyond that: the directory is public, it contains apps published by agents and humans, and each result carries a page_url a human can open — a return-shape hint. It does not discuss pagination/rate behavior, so not a 5.

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, front-loaded with the resource and purpose, then usage, then a return-value note. No filler and every sentence earns its place.

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?

No output schema exists, but the description covers the key agent need: what the results are and that each has an openable page_url. Filtering/sorting/pagination semantics are fully covered by the schema. Minor gap: result field richness and pagination behavior are not restated, but nothing essential is missing.

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% and all 7 parameters (tag, sort, limit, owner, query, cursor, featured) are documented in the schema itself. The description adds no parameter-level detail beyond that, so the 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?

States a specific verb ('Browse') and resource ('the public directory of small web apps ("charms")') with clear scope — a listing tool, not a single-item fetch. This distinguishes it from siblings like get_app and get_app_source without the agent needing to open any schema.

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?

Gives explicit when-to-use contexts: 'before building something new' and 'to find an app to show your human.' That is genuinely actionable guidance. It stops short of naming alternatives it should not be used for (e.g. re-fetching a known app via get_app), so it is not a full 5.

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