client_listRetrieve all stored clients with their id, address, email, and VAT id in one read-only list. Use it to verify existing client records before creating invoices.
List every stored client with id, address, email and VAT id. No arguments, and it writes nothing. With none stored it says so: invoice_create also creates a client from the name you pass.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v0.20.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden. It discloses that the tool writes nothing (read-only), takes no arguments, and reports when no clients are stored. It also adds the useful side note that invoice_create can create a client from a name, which helps the agent understand the relationship. It doesn't mention pagination or ordering, but for a zero-argument list tool this is adequate.
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?
Three sentences, each earning its place: the first states the action and output fields, the second clarifies no-args and no-writes, the third covers the empty case and a relevant alternative. No fluff, front-loaded with the core purpose.
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 zero-parameter, read-only list tool with no output schema, the description is nearly complete. It covers the return fields, the empty case, and the no-write guarantee. The only minor gap is not describing the output format (e.g., array vs. object) or ordering, but that's not critical for a simple list tool.
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 schema has zero parameters and 100% coverage, so the baseline is 4. The description reinforces this by explicitly stating 'No arguments', which removes any ambiguity. It also adds meaning by describing what the output contains (id, address, email, VAT id), which is beyond the empty schema.
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 resource ('every stored client'), and enumerates the exact fields returned (id, address, email, VAT id). It also distinguishes itself from sibling tools by noting it takes no arguments and writes nothing, which clearly separates it from client_add and client_delete.
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 explicitly says 'No arguments' and 'writes nothing', which tells the agent when to use it (when you need a read-only list of all clients). It also mentions the empty-case behavior and points to invoice_create as an alternative for creating a client from a name, though it doesn't explicitly say 'use this instead when...' for other siblings.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.