list_agencies

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

With no annotations, the description carries the burden of behavioral disclosure. It states the scope accurately, including the non-FDSN-wired behavior, but does not explicitly state that this is a read-only, side-effect-free operation or describe ordering/pagination. The behavior is largely inferable from the word 'list', but not fully explicit.

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?

The description is a single concise sentence with no filler. It front-loads the core purpose and adds one meaningful qualifier about FDSN-wired inclusion, which is exactly the kind of information an agent needs without any waste.

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?

Given the tool's low complexity, zero parameters, and existing output schema, the description is sufficient for an agent to invoke it correctly. The only additional context that might help would be usage guidance, but the simplicity of this list operation makes that a minor omission.

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 has zero parameters and the schema is empty, so there is no parameter semantics for the description to clarify. The baseline for a zero-parameter tool is 4, and the description does not introduce any unnecessary parameter-related content.

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?

The description clearly identifies the resource ('all agency codes') and the action (listing them). The parenthetical '(whether FDSN-wired or not)' adds a valuable scope distinction that separates this from any FDSN-only agency list or agency-specific tools like get_agency_info.

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?

The description implies when to use the tool: when you need the complete set of agency codes known to the server. However, it does not explicitly mention alternatives or exclusions, so an agent could still wonder whether get_agency_info or list_recent_by_agency would be more appropriate for a given request.

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