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

With no annotations, the description carries the full burden. It does disclose a meaningful behavioral trait: 'Values discarded.' However, it does not explain what output is returned, whether the tool-call arguments themselves are the JSON object counted, or how optional parameters affect the result. This is partially transparent but incomplete.

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 extremely concise—two short sentences with no filler. 'Count keys in a JSON object' is front-loaded and direct. The brevity is a strength, though it sacrifices some necessary context.

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?

This tool has nine optional parameters, no required parameters, no annotations, and no output schema. The description does not explain how to construct the JSON object to count, whether empty calls are valid, or what the response represents. It is too sparse to be fully usable without additional inference.

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 baseline is 3. The description adds the general principle that values are discarded, which is useful. But it does not clarify how the nine parameters relate to the 'JSON object' being counted, and some parameter descriptions suggest unrelated behaviors like normalizing URLs or weather hints.

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 specific operation—'Count keys in a JSON object'—and clarifies that values are not used. This is not a tautology of the tool name. However, it does not explicitly distinguish itself from siblings or specify whether the JSON object is the tool-call arguments or a value in the 'json' parameter.

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?

There is no guidance on when to use this tool versus alternatives like validate-json or search-query-len. The description does not mention conditions, exclusions, or related tools. A minimal 'when you need to count keys' implication exists, but no real usage guidance is provided.

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