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

The description describes the merge behavior (deep-merge with overlay), which is adequate for a simple operation. However, it does not disclose whether inputs are expected as JSON strings (as schema implies) or already parsed objects, nor does it mention side effects, output format, or error handling. With no annotations, the description carries the full burden but leaves gaps.

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 that front-loads the key concept 'deep-merge'. Every word serves a purpose, and there is no unnecessary repetition or verbosity.

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 simple tool with no output schema and no annotations, the description is too brief. It omits output format (likely a JSON string), validation of inputs, and differentiation from siblings like json_merge_patch. The agent lacks enough context to confidently use the tool without guessing.

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?

The schema has no descriptions for parameters a and b (0% coverage), and the description only mentions 'two JSON objects' without explaining that inputs must be JSON strings or providing format details. This adds little meaning beyond the schema's type field.

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 tool performs a deep-merge of two JSON objects, specifying that the second overlays the first. This is specific and includes the verb 'merge' and resource 'JSON objects', but does not explicitly differentiate from the sibling json_merge_patch, which follows a different RFC.

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?

No usage guidance is provided. The description does not indicate when to use this tool versus alternatives like json_merge_patch or json_equal, nor does it mention any prerequisites or conditions for use.

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