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

Annotations already declare readOnly=false, idempotent=true, destructive=false, but the description adds real value: it clarifies the side-effect boundary (no copy, follow, or publish) and confirms idempotency across retries, which is useful retry context. It does not describe the result or any permission failure modes.

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?

Four short sentences, front-loaded with the core action and destination, then id source, then exclusions, then idempotency. No filler or repetition.

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 single-item save with no output schema, the description covers purpose, preconditions, side effects, and idempotency, which is nearly everything needed. The only gap is the absent return-value description and the lack of disambiguation from add_saved_item.

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%, so the schema already documents both itemId and the optional list parameter, including the cross-list rejection rule. The description restates the id source (and even lists a slightly different set of tools than the schema) without adding format or constraint detail beyond it. Baseline 3 applies.

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 specific verb and resource ("Save one pick ... to Library under Saved picks") and scopes it to a single pick from any readable list. However, it does not distinguish itself from the closely-named sibling add_saved_item or from save_list, so an agent cannot fully disambiguate from the description alone.

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?

Provides clear preconditions ("a list you can read, yours or anyone's") and points at the id source (get_list_items or list_items), plus explicit exclusions ("Does not copy the pick, follow or publish"). It stops short of naming when to prefer this over add_saved_item or save_list.

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