Prepare library brief input

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

Goes well beyond the readOnly/idempotent annotations: it discloses the exact return shape (job_key, input_hash, bound revisions, counts, coverage, up to 20 work rows, five Librarian cards), a hard size cap of 24,576 bytes, and the side-effect fact that 'No work lease is acquired'. That last point is material because the sibling claim_library_work does acquire leases.

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?

Front-loads purpose, then alternatives, then return shape, then handoff — a sensible order. The middle clause listing return fields is dense and could have been split, but no sentence is filler given there is no output 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?

With no output schema, the description carries the return-value burden itself and does so (fields, row/card caps, byte limit). It also covers the prerequisite (a valid run_id from an assignment) and the required follow-up call, leaving nothing essential unstated.

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%, with both parameters fully documented including the YYYY-MM-DD format and non-future constraint. The description adds only that the packet is 'dated' and tied to a requested brief, which maps onto the date param but supplies no new syntax or edge-case detail beyond the schema.

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 ('Prepare a dated library-status packet') and scopes it to a specific consumer ('a brief that the client writes'). It also names the two sibling readers it is not (get_library_activity, get_playbook_input), so an agent can discriminate 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 an explicit when ('Use for a requested daily brief'), explicit when-not alternatives with their differentiating conditions ('direct metrics' vs 'topical research'), and a downstream instruction ('Pass the unchanged packet to publish_library_brief after writing').

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