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

Beyond the readOnly/openWorld/idempotent hints, the description discloses caching duration (ten minutes), cost (0 credits, no cold-fetch allowance), and a separate quota of 30 requests per IP per day shared across channels and playlists that counts cached reads and resets at midnight UTC. These are exactly the operational facts an agent needs and they are not derivable from annotations or schema.

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?

Scope and cap come first, then cost and quota, then input constraints, then the inventory caveat and an example prompt. Every sentence carries distinct information with no restatement of the name or title.

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?

The tool has only two mutually exclusive parameters and an output schema, so return-value explanation is unnecessary. The description covers the result cap (15 entries), freshness model (RSS, ten-minute cache), quota exhaustion, and input resolution requirements, which is 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 already 100%, so the baseline is 3, but the description adds real meaning: it states that exactly one of channel or playlist applies and that an unresolved handle is not accepted for the channel parameter. The only missing detail is what an "already-resolved alias" looks like syntactically, which the schema also omits.

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 opens with a specific verb and resource plus hard scope limits: "Read up to the newest 15 public RSS entries from exactly one channel or playlist." The clause "This is a recent window, not a complete inventory" implicitly separates it from list_videos, but no sibling is named outright, so the differentiation requires a small inference.

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?

It gives a clear precondition for calling ("Use a UC channel ID, an already-resolved channel alias, or a public playlist ID/URL") and warns that "an unknown handle must first be resolved on the keyed API." That is actionable context, though it stops short of saying when to prefer list_videos or the other siblings instead.

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