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

Far beyond the single readOnlyHint=false: it discloses snapshot semantics ('the values are copied into the project, and later stock edits do not change a card already placed'), cost ('Free'), the shape of the result (clip, track, text shown), and an exhaustive enumerated set of refusal conditions with the fix for each (retired item, missing sell_price_cents, missing currency, missing namespace, locked/unknown/non-text track, overlap with nearest-fit start_ms). This is exactly the operational context annotations cannot carry.

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 action in the first clause, then behavior, then style options, then the refusal list — a logical order. It is a dense paragraph rather than scannable structure, and the style layouts partly overlap the enum, but nearly every sentence carries actionable information.

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 7-parameter mutation with no output schema, the description covers inputs, defaults, side effects, return shape, cost, and all failure modes with remediation. An agent has everything needed to call it correctly and to interpret refusals without further tooling.

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 still adds value by explaining what each style actually renders and where ('tag: name over price, lower left', 'banner: one line, bottom centre', 'price_only: price alone, large, top right') and by tying currency to the business sales_settings default. It also connects stock_item_id and track_id to their resolving tools.

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?

Opens with a concrete verb and resource ('Put a stock item's name and selling price on the video as a product card') and then specifies exactly what is created: a price_tag text clip on the first text track. It also names the sibling it is distinct from (studio.place_product_card for raw values), so an agent can separate the two without opening either 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 routing context: requires a stock item id (stock_item_list for ids) and a token with the stock namespace, and explicitly names studio.place_product_card as the fallback when you want to pass values yourself. It does not spell out a full when-not-to-use-this-tool rule, but the alternatives are surfaced inline.

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