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

Annotations indicate readOnlyHint=false and destructiveHint=false, and the description adds meaningful behavioral detail beyond that: it mutates the library, feeds personalization signals, is idempotent, and requires SF_API_KEY. This gives the agent important operational expectations without contradicting the annotations.

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 efficiently structured: main action first, then mutation warning, personalization effect, idempotency, auth requirement, and a pointer to the relevant alternative. Every sentence contributes useful information without redundancy.

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 single-parameter, side-effecting tool with an output schema and annotations, the description covers the essential context: what it does, side effects, idempotency, auth needs, and the closest alternative. Nothing critical is missing 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?

There is only one parameter, arxiv_id, and the input schema already describes it fully with an example. The tool description does not add extra parameter-level detail, so a baseline score of 3 is appropriate when the schema carries the semantic load.

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 uses a specific verb and resource: 'Save a paper to the authenticated user's Scholar Feed library (bookmark).' It clearly frames the operation as creating a bookmark and even distinguishes it from the sibling add_to_collection, which performs a save plus collection filing. This leaves no ambiguity about what the tool does.

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 clearly states when to use save_paper: to save/bookmark a paper in the Scholar Feed library. It also names an alternative, add_to_collection, and gives the condition for choosing that instead ('to file it into a named collection in one step'). It does not explicitly exclude other related siblings like like_paper, but the context is clear enough.

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