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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive. The description adds valuable network-level behavior ('CF-robust' with direct fetch and proxy fallback) and normalization, which are not captured in annotations. No contradictions.

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 sentences with no filler. The core purpose and scope are front-loaded, followed by a critical technical note and a usage hint. Every word earns its place.

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 fetch tool with three well-documented parameters and annotations covering safety, the description is nearly complete. The only gap is that it does not describe the return format or whether it returns normalized items, but this is minor given the tool's simplicity and the presence of sibling tools that may clarify expected output.

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 all three parameters (url, limit, query) are already documented with types and ranges. The description adds no additional parameter-level detail beyond the schema, which meets the baseline for high coverage but does not exceed it.

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 states a specific verb ('fetch') and a resource ('any RSS / Atom / RDF feed') with an explicit normalization behavior. It clearly differentiates from siblings like list_feeds (curated sources) and read_feed (likely a different read operation) by emphasizing arbitrary URL fetching.

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?

The description explicitly directs the agent to use list_feeds first for curated sources, providing a clear alternative. However, it does not explicitly contrast with read_feed, which is a close sibling; a note about when to prefer fetch_feed over read_feed would make it fully explicit.

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