MCP Action Firewall

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

No annotations are provided, placing full burden on the description. While it states the tool 'Returns' a value (implying read-only), it lacks explicit safety disclosure, return format details (number vs string), or error behavior that would be essential for an unannotated 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 a single, efficient sentence with no redundancy. It is appropriately front-loaded with the action verb. However, given the lack of annotations, extreme brevity leaves gaps that a slightly longer description could have filled.

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 low-complexity tool (2 parameters, simple operation) with complete schema coverage, the description provides the minimum viable contract. However, the absence of annotations and output schema means critical behavioral details (return type, safety guarantees) are missing.

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 ('a' and 'b') fully documented in the schema. The description adds minimal semantic value beyond the schema, mentioning 'two numbers' generally, which aligns with but doesn't extend the parameter documentation.

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 (Returns) and resource (sum) with input requirements (two numbers). While it doesn't explicitly differentiate from siblings (like echo or get-env), the mathematical operation is distinct enough that the purpose is 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 provides no guidance on when to use this tool versus alternatives, nor does it mention prerequisites or constraints (e.g., number types, overflow behavior). With siblings like echo available, some context on when summing is appropriate would be helpful.

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