ARCA invoice session status

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

With no annotations, the description carries the behavioral disclosure burden. It explicitly states the tool reads and 'Does not mutate ARCA,' which is a meaningful guarantee given the sibling tools mutate state. It does not detail the exact return format, but 'Read whether' makes the primary behavior clear enough.

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 short sentences, front-loaded with the core purpose and followed by a concise safety note. Every word earns its place; there is no redundancy or 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?

For a parameterless status-check tool with no output schema, the description is nearly complete: it names what is being checked and explicitly states the operation is non-mutating. It could be improved by spelling out the return shape (e.g., boolean), but the phrase 'Read whether' makes the expected result reasonably inferable.

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 schema coverage is 100%, so there is nothing missing. The description adds useful context about the subject ('local ARCA session'), which earns credit above the baseline for an empty-parameter tool.

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: 'Read whether the local ARCA session has a prepared invoice.' This clearly distinguishes it from the mutating siblings (prepare, issue, discard) and from listing invoices, by scoping to the local session's prepared invoice state.

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 it: when you need to know whether a prepared invoice exists in the local ARCA session. It does not explicitly name alternatives or exclusions, but 'Does not mutate ARCA' provides useful context that this is a safe read-only check relative to the mutating siblings.

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