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

Annotations already declare readOnly, idempotent, non-destructive, openWorld=false. The description adds valuable context beyond them: it returns plain links (name + homepage URL only), never fetches sites itself, and caps at 50 per call. It stops short of covering pagination or rate limits, so it's strong but not exhaustive.

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 sentences, front-loaded with the core behavior, then usage routing. Every sentence earns its place with no redundancy.

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?

Though there's no output schema, the description specifies the return shape (name and homepage URL only) and the no-fetch behavior. Combined with high schema coverage for filters, an agent has everything needed to call it correctly.

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 88%, so parameters are already well-documented. The description adds only 'Same filters as search_sites' and 'up to 50 at a time', which lightly reinforces the limit max but doesn't enrich semantics beyond the schema. 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 and resource: 'List real SaaS marketing websites as plain links: name and homepage URL only.' It also implicitly distinguishes itself from search_sites and get_site by noting it returns links only. An agent can identify the tool without opening the 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?

Clearly states when to use it ('when you want a batch of live sites to open and study yourself in a browser'), a key exclusion ('this server never fetches them'), and routes to alternatives ('use search_sites or get_site for palettes, fonts, stacks and sections'). This is explicit when/when-not/alternative guidance.

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