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

With no annotations, the description carries the full burden and mostly fails: it doesn't say whether registration is idempotent, how external_ref or deadline_desk_receipt_id affect deduplication, or whether the loop can later be modified. 'Returns TRACE receipt' is the only behavioral disclosure, and it is unexpanded.

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?

Two short sentences, front-loaded with the action and the valid kinds. Nothing is wasted, but the brevity comes at the cost of specification rather than being achieved alongside it.

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?

A 9-parameter mutation tool with no annotations, no output schema, and 11% schema coverage needs substantially more description than two sentences. The undeclared TRACE receipt format and undocumented optional parameters leave real gaps for correct invocation.

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 11% (only due_at), and 9 parameters exist, yet the description only restates the kind enum that is already in the schema. Counterparty, amount_cents, currency, source_url, external_ref, notes, and deadline_desk_receipt_id are left with no explanation anywhere.

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 (Register) and resource (open loop) and enumerates the valid kinds, so the agent knows this is a creation tool for tracked obligations. It doesn't explicitly contrast with siblings get_loop and list_due, but the verb alone is enough to separate creation from retrieval.

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?

No statement of when to use this versus list_due/get_loop, no prerequisites, and no guidance on what makes something an 'open loop' worth registering. The agent must infer usage entirely from the name.

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