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

Annotations already flag this as a non-readOnly, non-idempotent mutation; the description adds real value on top by disclosing reversibility ('the shelf as it was is kept: undo_shelf_change puts it back') and an auth requirement ('needs an access token that can read and change your records'). It omits the duplicate-add behavior implied by idempotentHint=false, but the key behavioral facts are covered.

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, purpose front-loaded, each sentence carrying distinct information (what it does, its role, reversibility, auth). Slightly dense phrasing in the first clause but 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 single-param mutation with no output schema, the description covers purpose, downstream role, reversibility and auth, which is close to everything an agent needs. It doesn't state the return shape (e.g., what's confirmed after the add), the one remaining minor gap.

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 coverage is 100% and the single param is documented as 'The materials, by name.' The description still adds meaning by clarifying that names may be the library's names or the user's own materials, which helps an agent supply valid values rather than guess.

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 (marks materials as on hand) and resource (materials/shelf), and defines the fuzzy term 'on hand' by tying it to the sibling capability 'Match with what I have'. It also distinguishes itself from undo_shelf_change, so an agent can place it in the family without opening schemas.

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?

Gives clear context for use (populating the shelf that match_with_what_i_have reads from) and points to undo_shelf_change as the reversing action. It stops short of an explicit when-not-to-use or a contrast against add_my_material, but the usage situation is unambiguous.

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