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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds useful behavioral context by specifying the exact return fields (name, description, subscriber count) and sort/filter capabilities, going beyond 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 efficient sentences, front-loaded with the core action. Every clause adds value (default instance, sort/filter options, return fields) with no redundant wording.

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 read-only list tool with an output schema, the description covers the essential aspects: purpose, default instance, sort/filter options, and return fields. It could mention pagination behavior of page/limit, but the output schema plus annotations make it sufficiently complete. Not perfect, but solid.

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 has 0% parameter descriptions, so the description must compensate. It explains the semantics of 'sort' (Active/Hot/New/TopMonth/etc.), 'type_' (All/Local/Subscribed), and 'instance' (default lemmy.world), but does not address 'page' or 'limit', which are non-obvious. Partial guidance, so baseline 3.

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 clearly states the tool's function: 'List communities on a Lemmy instance', with specific sorting and filtering options. It distinguishes from the sibling tool 'community' (singular) by explicitly pluralizing and listing features.

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?

Provides clear context for when to use the tool (listing communities), including default instance and available filters/sorts. However, it does not explicitly mention alternatives or exclusions, such as when to use 'community' instead.

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