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

With no annotations, the description carries the full burden and delivers notable behavioral detail: it costs 3 credits whether cached or not, and a failed call is refunded — genuinely useful for an agent budgeting calls. It omits authorization requirements and any caching/rate-limit nuance, keeping it from 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 tight sentences: purpose and returned fields first, then the related resource and the parameter constraint, then cost. Every sentence earns its place with no padding.

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 simple single-entity fetch with full schema coverage and no output schema, the description covers purpose, returned fields, the parameter constraint, the related posts path, and cost/refund behavior. Nothing essential to invoking it correctly 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 coverage is 100%, so the baseline is 3, but the description adds the important constraint 'Give exactly one of `url` or `id`' — a mutual-exclusion rule not expressed in the schema (required is empty, no oneOf). This is real added value over 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?

States a specific verb and resource ('Fetch one community') and enumerates the returned fields (name, description, member_count, created_at, join_policy, rules, creator), making it unambiguous. It also names the complementary `x/posts` with `community_url` path, distinguishing community metadata from community posts.

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?

Clarifies the boundary: this tool returns the community, while `x/posts` with `community_url` returns its posts, and it instructs to give exactly one of `url` or `id`. It provides clear context but stops short of stating when this tool should be preferred over, or is a prerequisite for, other X tools.

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