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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds real value beyond that by naming the returned state values (SCHEDULED, NEW, SENT, CANCELED) and the fields returned, which is useful since no output schema exists. It does not mention not-found/error behavior, keeping it from a 5.

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?

One sentence, front-loaded with the operation and the resource, followed by the identifier requirement and the returned fields. No filler and no 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?

With no output schema, the description usefully enumerates the returned fields (state, requested/filled times, medication, prescription, order), covering the return shape. The gaps are minor: no mention of lookup-failure behavior or how states relate to downstream workflows.

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% for the single fill_id parameter, including the 'fil_…' format hint, so the schema carries this dimension. The description adds no syntax or validation detail beyond what the schema already provides; 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?

Specific verb (Get) plus resource (one fill) with an inline definition of the domain term — 'a single dispensing of a prescription within an order' — which distinguishes it from the sibling get_prescription and get_order resources. An agent can tell exactly what entity this returns without opening the schema.

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?

'by id' implies the tool is a lookup keyed on a known fill id, so usage is inferable. However, it never states when to prefer this over list_prescriptions/get_order or where a fill id comes from, and gives no exclusions or prerequisites.

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