list_purchases

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

Annotations already cover readOnlyHint and openWorldHint, but the description adds material the annotations cannot express: that an unknown name is an error listing what exists, and that without the Gryzzly budget offer every call returns no_permission. It does not discuss response shape or pagination behavior, which keeps it short of 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?

Five tight sentences, front-loaded with purpose and definition before alternatives, permissions and filter behavior. No filler and nothing that restates the title.

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?

An output schema exists, so return values need no explanation; with annotations plus output schema, the description supplies the remaining gaps an agent needs — sibling routing, permission gate, and filter error behavior. Complete for a read-only filtered list tool.

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%, so the baseline is 3; the description adds marginal value by restating that filters accept project and task names, codes or ids and by specifying the failure mode for an unknown name. It says nothing about limit/offset semantics, which the schema already documents, so it does not fully escape the baseline.

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, defines what a 'purchase' is (extra costs such as licences or subcontracting), and distinguishes itself from get_purchase by contrast. An agent can tell it apart from the many sibling list_* tools without opening a 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?

Gives explicit use cases ('review what a project cost beyond time') and names the alternative plus the condition that selects it ('use get_purchase when you already hold one purchase id'). It also flags the permission prerequisite, so the agent knows when this call is even viable.

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