library_save

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

With no annotations, the description carries the transparency burden. It discloses key behaviors: idempotency ('saving the same paper again updates only the fields you pass and never duplicates') and the deletion limitation. These are important side effects not inferable from the name or schema.

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 sentences, front-loaded with the core purpose, then examples, then key behavioral caveats. Every sentence earns its place with no filler.

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 5-param tool with no output schema, the description covers purpose, usage, idempotency, and deletion constraints. It does not mention authentication or return values, but these are not essential for tool selection. The lack of explicit reference to the item_id coming from a prior search is compensated by the schema.

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 documents all 5 parameters with descriptions, so baseline is 3. The description's natural-language examples ('note that', 'mark as read') map to note and reading_status, but add little new semantic detail beyond the schema. The partial-update note is behavioral rather than parameter-specific.

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 opens with 'Save (or update) a paper in the user's personal arXivSub library', using a specific verb+resource. It clearly distinguishes from siblings like search_papers and library_list by focusing on persistence into the user's library. The example intents further pin down the purpose.

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?

Explicit usage phrases are given: 'save this', 'bookmark that paper', 'add it to my <X> collection', 'note that ...', 'mark as read'. It also states a clear non-use case: 'Cannot delete — removals are done on the website.' This provides strong when-to-use guidance without needing to name alternatives.

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