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

With no annotations, the description carries the full burden and does disclose a real output behavior: encrypted sides 'report locked instead of contents,' which the agent cannot learn from the schema or output schema alone. It leaves unstated whether the tool is strictly read-only and what happens if an id is missing or invalid, so it stops short of full behavioral disclosure.

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 short sentences, front-loaded with the core action, then the routing guidance, then the edge-case caveat. There is no filler or repeated 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?

The output schema covers the return shape and the schema covers both parameters, so the description is nearly complete for a two-arg read tool. Minor gaps remain around failure behavior for unknown ids and the meaning of diff direction.

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 coverage is 100% and both UUID parameters are already documented in the schema, so the baseline is 3. The description adds only that these are saved calculations being compared, which is already implied, and does nothing with directionality (whether A is the baseline and B is the comparison).

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?

States a specific verb and resource ('Diffs two saved calculations') and narrows the scope to inputs and results field by field. It also implicitly separates itself from load_saved_calculation, which the agent would otherwise need to reason about.

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?

Gives an explicit use case ('compare my mortgage before/after' style questions) and an explicit alternative to avoid ('instead of reconstructing the diff from two loads'). The selection condition between this tool and the sibling load_saved_calculation is unambiguous.

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