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

Annotations already declare idempotentHint=true, destructiveHint=false, and readOnlyHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the caller becomes the first member with role admin, and currency is locked permanently after creation.

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 tight sentences with zero filler, front-loading the core action before the side effects and the currency constraint. Every clause adds information.

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. For a simple four-parameter create, the description covers the essential side effects and the immutability constraint; only edge cases like duplicate names or retry behavior with idempotency_key are 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 description coverage is only 25% (just idempotency_key), so the description must compensate. It explains currency well (ISO 4217, examples, immutable later) but leaves name and the optional description parameter unaddressed, including whether names must be unique.

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 ('Create a shared-expense group'), which is immediately distinguishable from siblings like join_group, update_group, and archive_group. It does not explicitly name those siblings, but the purpose is unambiguous.

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?

Usage is implied by the verb: use this to start a new group. However, it offers no explicit when/when-not guidance, such as when to create a group versus join_group with an invite, or any precondition about needing an existing account.

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