chapter_bookmarks

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

No annotations are provided, so the mention 'pure sidecar' and 'zero API calls' is valuable behavioral disclosure. The description also discloses persistence location ('local sidecar') and the save/list/delete operations, which behave like CRUD with no external effects. It does not mention dry_run behavior, response format, or whether delete requires an existing bookmark, but those are partially covered by the schema. No contradiction with annotations (none exist).

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 three short sentences, each earning its place. The first sentence states scope and storage, the second lists operations and the consumer tool, and the third states the 'zero API calls, pure sidecar' behavior. It is front-loaded with the purpose rather than boilerplate. There is no filler, repetition of the title, or restatement of the schema.

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?

The tool has 7 parameters but 0 required, an op enum, a dry_run flag, and no output schema. The description covers the key context an agent needs: the tool is local-only, has three operations, and is designed for later jumping. It does not explicitly state return shapes or how errors surface (e.g., deleting a nonexistent bookmark), but those are not common in tool descriptions and the schema already documents the parameters. A stronger description might note whether 'save' overwrites an existing label, but the overall context is sufficient for correct invocation.

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 high at 86%, so the baseline is 3. The description adds meaningful operational context: it explains that the operation is 'pure sidecar' and that save/list/delete are the supported ops (matching op enum), and it names the related jump_to_chapter tool that consumes stored bookmarks. It also clarifies which parameters are required per operation contextually (label for save, book_uri for save/delete) beyond just the schema's minimal notes. It does not add meaningful detail about position_ms or chapter_name beyond what the schema already states.

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?

States a clear verb+resource combination: 'Named chapter+position bookmarks per audiobook, stored in the local sidecar' and names the three operations (save/list/delete). It explicitly differentiates from sibling jump_to_chapter by referencing it as the later consumption point. The description could slightly benefit from saying it is a local-storage utility rather than a Spotify API endpoint, but the next sentence 'Zero API calls — pure sidecar' makes that 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 description implies when to use it ('bookmarks per audiobook', 'jump later via jump_to_chapter') and clearly states it is a local sidecar operation, which helps distinguish it from API-backed siblings like get_audiobook or get_chapter. However, it does not explicitly say when NOT to use it or name alternative bookmark tools like list_playback_bookmarks, episode_bookmark, or save_scene. With no annotations covering usage, some exclusion guidance would have earned a 5.

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