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. It discloses key behavioral traits: it's a write operation (mutation), returns an updated expense object, and includes a caution note about careful use. However, it doesn't specify rate limits, authentication requirements, error conditions, or whether changes are reversible. The description adds meaningful context beyond what's in the schema but could be more comprehensive for a mutation tool.

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 efficiently structured in two sentences: first states purpose and parameters, second provides behavioral caution. Every sentence earns its place with no wasted words. It's appropriately sized and front-loaded with essential 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?

Given this is a mutation tool with no annotations and no output schema, the description does well by stating it's a write operation, listing updatable fields, and noting it returns an updated object. However, it could be more complete by specifying authentication needs, error handling, or what happens to unmentioned fields. For a 7-parameter update tool, it's reasonably complete but has minor gaps.

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 documents all 7 parameters thoroughly. The description lists the metadata fields that can be updated (memo, category, budget, department, location, custom fields), which aligns with parameter names but doesn't add significant semantic meaning 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 'update' and resource 'existing card expense' with specific metadata fields listed (memo, category, budget, department, location, custom fields). It distinguishes from sibling tools like 'get_expense' or 'get_all_expenses' by being a write operation rather than a read. However, it doesn't explicitly differentiate from potential update alternatives (none appear in sibling list).

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 'existing card expense' and the caution note about being a write operation, suggesting it should be used when metadata needs modification. However, it doesn't provide explicit guidance on when to use this vs. alternatives (no update alternatives in siblings), nor does it mention prerequisites like authentication or permissions. The caution note adds some guidance but isn't specific about alternatives.

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