Brex MCP Server

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

With no annotations provided, the description carries the full burden. It mentions 'supports expansion of nested objects' and 'returns complete card expense details with money annotation', which provides useful behavioral context about response format and expansion capabilities. However, it doesn't address error conditions, rate limits, or authentication requirements.

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 concise sentences with zero waste: first states core purpose, second adds expansion capability, third provides critical deprecation warning. The deprecation notice is appropriately placed at the end as critical information.

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 read operation with 100% schema coverage but no output schema or annotations, the description provides good context: purpose, expansion capability, return format hint, and critical deprecation status. The main gap is lack of output structure details, but the description compensates reasonably well given the tool's relative simplicity.

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%, so the schema already fully documents both parameters. The description mentions 'supports expansion of nested objects' which hints at the 'expand' parameter's purpose, but doesn't add significant semantic value beyond what the schema provides. Baseline 3 is appropriate 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 verb 'retrieve' and resource 'card expense', specifies it's for a single item by unique ID, and distinguishes it from the sibling 'get_expense' by noting this tool is deprecated in favor of that one. This provides specific differentiation from related tools.

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 'Deprecated - use get_expense instead', providing clear when-not-to-use guidance. It also distinguishes this from sibling tools by specifying it retrieves a single card expense by ID, not multiple expenses or other resources.

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