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

Annotations only supply readOnlyHint/openWorldHint, but the description adds substantial behavioral context: 10 posts per page newest-first, the q filter applies only within the current page, post bodies are excluded, no API key needed, and x402 pricing ($0.002/successful call, failures not charged). These are non-obvious traits an agent needs before invoking.

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?

Opens with the resource and data returned, then tacks on access/pricing details, so key information is front-loaded. It's a dense single run-on sentence, which is slightly hard to parse but nearly every clause carries useful information.

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?

Given an output schema already defines the return shape, the description still covers identification, pagination, filtering scope, access requirements, and cost—everything an agent needs to call it correctly. Nothing material 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 all three parameters are already documented in the schema, including the page-only scope of q. The description largely restates these constraints rather than adding syntax or format detail beyond the schema, so the baseline 3 applies.

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 resource (a beehiiv newsletter's post archive) and enumerates exactly what it returns: name, total posts, per-post title/subtitle/URL/publish time/authors/tags/reading time. This unambiguously separates it from the many other search_* verticals, which all target different sources.

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?

Explains the identifying key (beehiiv subdomain like superhuman, or the newsletter's own domain) and the page-based paging model, giving clear context for when this tool applies. It doesn't name exclusions or alternatives, but the sibling set is orthogonal source-specific searches, so this is a minor gap.

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