list_families

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered; the description's 'read-only and idempotent' restates that. What it adds beyond the annotations is the operational nature — 'pure in-memory introspection' — which tells the agent there is no network I/O or external side effect, plus the fact that it reports installation status per backing package.

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-loaded with the action and resource, then organized into clearly labeled 'When to use', 'Not for', and 'Behavior' segments. Every sentence carries routing or behavioral information; no filler.

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?

Zero parameters, rich annotations, and an output schema that carries the return shape, so the description's job is primarily routing and readiness semantics — both delivered. An agent has everything it needs to decide to call this and to interpret the result.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. Describing the return contents (capabilities, backing package, installed flag) is useful but belongs to output semantics rather than parameter meaning.

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 ('List every ISO 20022 family the gateway routes to') and enumerates the concrete families covered (pain, pacs, camt, acmt) plus what each entry contains. It clearly distinguishes itself from the schema-oriented siblings by naming 'search' and 'describe' as the tools for a different job.

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?

Explicit 'When to use' (check environment readiness, verify optional backing packages are installed) and an explicit 'Not for' that routes searching specific schemas to 'search' and 'describe'. Both the condition and the alternative are stated, leaving nothing to inference.

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