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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds real behavioral value beyond those hints: the sort order (followed shows first), the scope limited to this Mac, and the guarantee that each result carries both a local id and Apple's catalog id. These are return-behavior details the annotations cannot 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?

Three sentences, each earning its place: scope and ordering, the id pairing, and the bridge to public tools. The core capability is front-loaded in sentence one. Slightly verbose in the middle sentence with repeating 'which the other library tools take' / 'which every public tool here takes', but no wasted words overall.

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 two-optional-param read-only listing tool, the description is largely complete: scope, ordering, result contents, and the cross-tool usage pattern are all present. There is no output schema, and the description gives only a minimal account of each item's fields, leaving the agent to guess at additional metadata. This minor gap prevents a 5.

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 100% — limit and followed_only are already documented with their ranges and defaults. The description adds no parameter-specific guidance beyond the 'followed shows first' ordering, which relates to sort behavior rather than to the followed_only filter. Baseline 3 is appropriate since the schema carries the param semantics fully.

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 identifies the resource (every podcast in the Apple Podcasts library on this Mac) and the behavior (listing, with followed shows first), which distinguishes it from the public-catalog sibling tools. It explains the two id types the results carry, though the verb is implied rather than stated and no sibling is named explicitly, so it stops short of full disambiguation.

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 implies a workflow — obtain the local id from this tool, then hand it to the other library tools, and use the catalog id to cross over to charts, reviews, and feed. However, it never names alternatives like search_library or list_saved_episodes, and states no exclusion conditions, so an agent must infer when this tool is the right choice versus its library siblings.

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