Xero Expenses MCP

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

With no annotations provided, the description carries full burden but only mentions the draft requirement. It doesn't disclose other behavioral traits like whether this operation requires specific permissions, if it's idempotent, what happens on failure, or what the response looks like. For a mutation tool with zero annotation coverage, this leaves significant gaps in understanding its behavior.

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, efficient sentence that immediately conveys the core purpose without any wasted words. It's front-loaded with the essential information and doesn't include unnecessary details or repetition.

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 mutation tool with no annotations and no output schema, the description provides adequate basic context about the operation and its draft requirement. However, it doesn't address important aspects like error conditions, return values, or side effects that would be needed for complete understanding, especially given the tool's complexity as a write operation.

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 description coverage is 100%, so all parameters are documented in the schema. The description doesn't add any parameter-specific information beyond what's in the schema (like explaining format constraints or relationships between parameters). This meets the baseline expectation when schema does the heavy lifting.

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 states the specific action ('Add a line item'), the target resource ('to an existing DRAFT bill'), and the type of item ('expense'). It distinguishes from siblings like xero_create_bill (creates new bills) and xero_submit_bill (submits bills), making the scope and intent unambiguous.

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 states 'to an existing DRAFT bill', providing clear context about when to use this tool (only for draft bills). However, it doesn't mention alternatives like modifying existing line items or when not to use it (e.g., for submitted bills), and doesn't reference sibling tools directly for comparison.

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