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

Annotations only give readOnlyHint=false and openWorldHint=true, so the description carries the real burden and does: pricing tiers and minimums, required write scope, the $0.10/$0.25 per-minute model, the x402 keyless payment handshake including where the payment-required result and receipt appear, and the one-time collection_token disclosure. This is far beyond what annotations convey.

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?

The lead sentence front-loads the action, the return fields and polling guidance are compact, and the payment paragraph is dense but each clause is operationally necessary. It is a long block of prose rather than scannable structure, which costs it a point.

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 10-parameter, zero-required, no-output-schema, payable mutation, the description covers creation, cost, auth, keyless limits, idempotency, return values and the polling completion contract. Nothing an agent needs to call this correctly and interpret the result 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 the baseline is 3. The description adds meaning the schema does not: quote_id yields an exact quoted charge (400 if unknown/expired), keyless mode constrains input to one source and ≤3 videos, and quality defaults to whisper pricing. It does not document the url vs. urls vs. channel_url family split, which is the one real ambiguity left.

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 compound action — create a collection and start an ingest job for YouTube URLs — in one call, and names the HTTP mapping. The 'in one call' phrasing implicitly contrasts with the sibling pair create_collection + add_sources, so the agent can route without opening schemas.

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?

Explicitly routes the agent: use quote to lock a price and pass quote_id, poll get_status every 10–30 s until terminal status, and never pay again after a 409 or 502. It also states the keyless precondition (one channel-like source, at most 3 videos) that selects an alternate usage mode.

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