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

Annotations declare readOnlyHint=true and destructiveHint=false, so the safety profile is already known. The description adds valuable behavioral context beyond annotations: the one-hour link expiry, the instruction to show the link exactly as returned, the need to call again for a fresh link, and the Premium gating behavior with a clear error message. It doesn't mention rate limits or what happens if audio can't be generated, but the key behavioral traits are disclosed.

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 description is dense but well-organized. It front-loads the core function, then covers the Premium requirement, link expiry, and alternatives. Every sentence adds useful information. It's slightly long, but for a tool with this many behavioral nuances (Premium, expiry, sibling routing), the length is justified. The structure flows logically from what the tool does to how to handle the result.

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?

Given the tool's complexity (Premium gating, time-limited links, multiple output formats, sibling routing), the description covers the essential operational details. There's no output schema, so the description's mention of the download link and its one-hour validity is important. It could mention what the error response looks like for non-premium users, but it does say 'a non-premium account gets a clear message with a link explaining Premium,' which is sufficient for an agent to handle the failure case.

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 50%: the platform parameter is described in the schema ('anki gives an .apkg file, mochi gives a .mochi file'), but deckId has no schema description. The tool description compensates by explaining the file formats and the context of deck import, and it clarifies that the platform enum maps to specific file types. It doesn't add detail about deckId format, but the schema already constrains it (string, 1-64 chars). The description adds meaningful context about what the parameters produce.

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 clearly states the tool's function: 'Returns a download link for one of the user's decks as a file to import.' It specifies the resource (user's decks), the action (returns a download link), and the file formats (.apkg for Anki, .mochi for Mochi). It also distinguishes itself from siblings like get_deck and list_decks by noting that those are for text-import platforms like Quizlet and Brainscape.

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 provides explicit when-to-use guidance: 'Premium only; call it directly, without checking get_credits first.' It also gives clear alternatives: 'for them give the deck link from list_decks or get_deck' and 'Show the cards as text only as a fallback.' This is excellent routing information that tells the agent exactly when to use this tool versus siblings.

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