check_saved_items

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

With no annotations, the description carries full responsibility. It discloses the return format (boolean per URI) and the max count (40), which are useful. However, it does not explicitly state that this is a read-only, non-mutating operation, nor does it mention error behavior (e.g., invalid URIs) or authentication expectations. For a simple check tool this is adequate but not exhaustive.

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 two short sentences with zero filler. The core purpose is front-loaded, and the return-type note and limit are efficient additions. Every word earns its place.

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 a single parameter, full schema coverage, no output schema, and a straightforward behavior, the description provides all essential information: what it does, what it returns, and the maximum batch size. An agent can confidently invoke this tool without further clarification.

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 describes the 'uris' parameter fully (array of strings, max 40). The description adds value by stating 'Returns a boolean per URI', which implies an element-wise mapping to the input order — a semantic not present in the schema. This reinforces the limit and clarifies the correspondence between input and output.

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 states a clear verb and resource: 'Check whether items are saved in the user's library' and specifies the return type ('boolean per URI'). It distinguishes from siblings like get_saved_tracks (which retrieve full lists) and save_items/remove_saved_items (which mutate). The purpose is unambiguous.

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 intended use is implied: to verify if specific items are saved without retrieving the full library, but the description does not explicitly mention when to use it over alternatives like get_saved_tracks or check_following_artists. There is no when-not-to-use guidance, but the purpose is clear enough for an agent to infer the common scenario.

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