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

Annotations already declare readOnlyHint/openWorldHint/destructiveHint, so safety is covered; the description adds substantial context beyond that: the $0.0025 USDC per-call price paid inside the MCP call via x402 across four chains, the fact that x402 clients pay automatically, and a free sample invocation. This is exactly the kind of non-obvious operational behavior an agent needs.

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?

Front-loads the core purpose and return shape in the first sentence, then usage, then params and payment. The payment and sample details are dense but each sentence earns its place for a paid tool. Slightly verbose in the pricing/sample clause, but well ordered overall.

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, yet the description enumerates the returned item fields (title, link, published_at ISO 8601, summary without HTML, author, guid), covering the return contract. With annotations covering safety, params covering inputs, and the description covering returns and payment, nothing an agent needs to invoke this 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 description coverage is 100%, so both parameters are already documented. The description restates url (required) and limit (default 20, max 100) but adds no syntax, format, or edge-case semantics beyond the schema. Baseline 3 is appropriate when the schema carries the burden.

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 (fetch) and resource (RSS 2.0 / RSS 1.0 / Atom feed), enumerates the normalized JSON fields returned, and distinguishes itself from XML-parsing alternatives. An agent can tell this apart from sibling feed tools like feed_watch or news_search 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?

Gives clear usage context ('monitoring blogs, news sites, GitHub releases, podcasts or any feed URL'), which tells the agent when this tool is appropriate. However, it names no alternatives and gives no explicit when-not guidance, notably omitting how it relates to the similarly-named feed_watch sibling.

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