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

With no annotations, the description carries the behavioral burden. It usefully discloses that the tool is free (charged=false), does not fetch, and does not accept payment. It does not describe the output format, but the non-fetching and non-payment details are meaningful and go beyond the title.

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 sentences, each earning its place: purpose first, then cost/behavior, then routing to the alternative. The description is front-loaded and contains no filler.

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 3-parameter compare tool with no output schemaant, the description covers input semantics, cost/fetch behavior, and the sibling to use when conditions differ. The only notable gap is the lack of a description of the compare result format, but the operational context is sufficient for correct selection and invocation.

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%, so the schema already documents before/after as delivered batch JSON objects and fields as explicit field names. The description reinforces these ideas with 'already-held' and 'caller-named fields,' but adds no syntax or format details beyond the schema.

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 states a precise operation: comparing two already-held extract-batch JSON artifacts on caller-named fields. It uses a specific verb and resource, and differentiates itself from sibling extract_batch by highlighting that it is free and non-fetching.

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?

It explicitly tells the agent to use extract_batch when a paid observation is still needed and warns against adding a second paid diff. This gives a clear, actionable selection rule between this tool and its closest alternative.

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