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

The annotations already declare readOnlyHint=true and destructiveHint=false, so the agent knows this is a safe read operation. The description transparently discloses that the tool does not return the reading itself but only a link, which is a key behavioral aspect. It mentions that the interpretation is part of the paid service, which sets expectations. However, it doesn't detail rate limits, authentication, or what happens if spread is invalid, though such details are not required given the tool's simplicity.

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 a concise two-sentence block. It front-loads the core function (link to interactive spread) and efficiently explains the critical limitation (does not return interpretations). No word is wasted, and the em-dash style adds clarity. It earns a 5 for its structure and economy.

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 simple, read-only tool with full schema coverage and no output schema, the description is complete. It clearly states the tool's output (a URL) and the paid-nature context. It doesn't mention error cases or locale handling, but these are minor. Given the tool's simplicity and the support from annotations and schema, the description is sufficiently complete. A 4 is appropriate, slightly above average due to the clear scope restriction.

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?

The schema already covers 100% of the parameters with descriptions, providing a baseline of 3. The description adds context that the 'spread' parameter refers to a title or slug from list_spreads and that omitting it leads to a catalog, which goes slightly beyond the schema. The description text repeats the schema info but doesn't add parameter-specific semantics. Given full schema coverage, the description's implicit reference to list_spreads adds a bit more.

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 purpose: it provides a link to an interactive Tarot spread on Arcanika. It explains that cards are drawn and interpreted within the product, not returned by the tool. This distinguishes it clearly from tool functions that would return interpretations, distinguishing it from siblings.

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 explains what the tool does NOT do (does not return interpretations) and what it does (returns a URL for the user to perform the spread). It gives context that the interpretation is the paid part of the service. It doesn't explicitly name sibling alternatives, but the list of siblings (like get_card_meaning, list_spreads) provides alternatives; the description's clarification of scope is helpful. The guidance could be stronger by naming a specific alternative tool to use instead of asking for a reading.

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