Brex MCP Server

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

With no annotations provided, the description carries full burden and does well by disclosing key behavioral traits: it specifies that the tool returns 'complete expense details with money annotation' and 'Supports expansion of nested objects' with a list of expandable fields. This gives context about response content and optional functionality beyond basic retrieval. It doesn't mention error handling, permissions, or rate limits, but provides useful operational context.

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 two sentences that are front-loaded with core functionality and efficiently cover expansion support and return details. Every sentence adds value: the first defines the primary purpose, and the second explains optional features and output characteristics. No wasted words or redundancy.

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?

Given a read operation with 2 parameters, 100% schema coverage, and no output schema, the description is reasonably complete. It explains what the tool does, what it returns, and expansion capabilities. However, it lacks details on error cases (e.g., invalid ID handling) and doesn't explicitly confirm it's a safe read operation (though implied by 'Retrieve'), which would be helpful since annotations are absent. Overall, it covers most essential context for this tool type.

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%, with both parameters well-documented in the schema ('expense_id' as unique identifier, 'expand' as array of related objects). The description adds marginal value by listing the specific expandable objects (merchant, budget, etc.), which clarifies the enum options but doesn't fundamentally enhance understanding beyond the schema. Baseline 3 is appropriate as the 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 ('Retrieve'), target resource ('a single expense'), and key identifier ('by its unique ID'). It distinguishes from sibling tools like 'get_all_expenses' by specifying single-item retrieval rather than listing multiple items.

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 usage context through 'Retrieve a single expense by its unique ID,' suggesting this is for fetching specific known expenses rather than searching or listing. However, it doesn't explicitly state when to use alternatives like 'get_all_expenses' for bulk retrieval or 'get_expenses' (if that exists for different filtering). No explicit when-not-to-use guidance is provided.

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