List available provider types from the catalog with their configuration schemas.
| Name | Required | Description | Default |
|---|---|---|---|
| keys | No | Comma-separated provider keys to filter by | |
| name | No | Substring match on provider name | |
| channel | No | Filter by channel type (email, sms, push, etc.) |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The readOnlyHint annotation is present, so the read-only nature is already known. The description adds the useful detail that the output includes configuration schemas, which goes slightly beyond the annotation. However, it does not disclose any other behavioral aspects such as pagination, ordering, or default behavior, leaving the burden partially unmet.
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 that clearly states the primary function without any fluff or irrelevant details. It is front-loaded with the core action and resource, making it easy for an agent to parse quickly.
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?
For a simple listing tool with only optional filters and no output schema, the description captures the essential functionality. It mentions the catalog and schemas, which is the core output. It does not specify response format or pagination, but given the simplicity and the presence of parameter descriptions in the schema, this is a minor gap rather than a critical one.
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 100%, meaning all three parameters (keys, name, channel) already have descriptions in the input schema. The tool description adds no extra meaning or clarification about these parameters, so it does not go beyond the baseline expected when the schema is complete.
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 states a specific verb ('list') and a clear resource ('available provider types from the catalog'), and additionally notes that the result includes configuration schemas. It is not explicitly differentiated from the sibling 'list_providers', but the catalog concept and schema mention give enough distinction for an agent to understand the tool's role.
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 guidance is given on when to use this tool versus alternatives like 'list_providers' or 'get_provider'. The description does not mention any context, prerequisites, or exclusions, so an agent has no way to decide between this and similar listing tools without inferring from the name itself.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Tools are mostly organized as distinct resource/action pairs, but several clusters are easy to confuse: list subscription tools (add_subscribers_to_list vs bulk_subscribe_to_list vs subscribe_user_to_list), message vs message-content vs message-history retrieval, and the many journey/journey-template list/get tools. Detailed descriptions rescue most selections, but the sheer number of near-identical verb/resource names creates real misselection risk.
Almost all tools follow a snake_case verb_noun pattern (create_, get_, list_, replace_, send_, publish_, archive_). Minor deviations keep it from a perfect score: courier_installation_guide is noun-first, and add_bulk_users sits awkwardly next to the bulk_add_* family, but the overall convention is predictable and readable.
144 tools is an extreme working-set size for an agent to hold and choose from, far beyond the reasonable 3–15 range. Even for a broad platform like Courier, this should be split into focused sub-servers (templates, journeys, users, lists, preferences, etc.) to remain usable.
The surface is remarkably comprehensive, covering sending, templates, journeys, automations, users, tenants, lists, preferences, providers, routing, brands, audiences, translations, digests, bulk jobs, and audit events. Notable gaps exist—automation template CRUD and digest schedule management are missing—but most workflows can still be completed with workarounds.
