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

The annotations already establish read-only, idempotent, open-world, non-destructive behavior, so the description's job is to add beyond that — and it does, disclosing a Cloudflare-robust fetch path with proxy fallback when a source blocks the gateway. That is real runtime behavior an agent could not infer from annotations. It does not cover failure modes (what happens if both direct and proxy fail) or latency/rate characteristics.

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 short sentences, front-loaded with the core action, then the reliability trait, then the sibling routing hint. No filler and nothing buried.

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, so the description should hint at what comes back; it says 'normalize' but never indicates the returned structure (items with title/summary, ordering, whether fetch metadata is included). Combined with the unresolved overlap with read_feed, an agent has enough to call it but not full confidence in the result shape.

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%, with url, limit range/default, and query all documented in the schema, so the schema carries the parameter burden. The description adds nothing further about parameters — no note on how query interacts with normalization or what happens when limit exceeds feed size — so 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 verb and resource (fetch and normalize RSS/Atom/RDF feeds by URL), including the supported formats, which is concrete. It routes against list_feeds but never distinguishes itself from the sibling read_feed, which from the name alone appears to serve a very similar purpose — that ambiguity keeps it below a 5.

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?

"Use list_feeds first for curated sources" gives an explicit alternative and the condition that selects it. However, there is no guidance on when to prefer fetch_feed over read_feed, nor any exclusion for cases where this tool is the wrong choice.

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