An agent’s JSON file can fail in two different ways: it may not be valid JSON, or it may be valid JSON that the agent does not accept. A parser checks the first problem; the specific agent’s documentation or schema is needed for the second. Because no agent is named here, there is no universal set of configuration keys or paths to prescribe.
When does an agent JSON file break?
It breaks when the text cannot be parsed as JSON, when the parsed value does not match the agent’s expected configuration, or when the application cannot accept the file at its size, nesting depth, encoding, or supported version. These are separate failure points: passing a syntax check does not prove the agent can use the file.
When the text is not valid JSON
JSON has a defined grammar. A missing comma, an extra comma, an unquoted property name, an invalid literal such as True instead of true, or a malformed string escape can prevent parsing. These are examples of grammar errors, not a claim about how often any particular agent encounters them.
Run the file through a JSON parser or validator to identify syntax problems. RFC 8259 requires parsers to accept texts that follow the grammar, but permits implementations to accept extensions as well. As a result, a permissive tool may accept text that a stricter parser or the target application rejects. For portability, use standard JSON rather than relying on extensions. See RFC 8259.
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When valid JSON has the wrong structure
A successful parse establishes only that the document is a JSON value. It does not establish that an agent recognizes its keys, accepts its nesting, or allows the supplied value types. For example, a syntactically valid string where the application expects an array is still the wrong configuration.
Check the documentation or schema for the exact agent and version you use. Without that information, it is not possible to give reliable universal key names, file paths, or migration instructions.
When duplicate keys or key order cause trouble
Keep each object’s member names unique. RFC 8259 says names within an object should be unique and warns that receiver behavior is unpredictable when they are not: an implementation might keep the last value, reject the object, or expose multiple values. T. Bray, editor and author of RFC 8259, states: “When the names within an object are not unique, the behavior of software that receives such an object is unpredictable.”
Do not depend on object member order unless the target application explicitly documents that requirement. Implementations can differ in whether that order is visible to the software using the parsed data.
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When a parser’s size or depth limits matter
A parser may limit the total text size or how deeply objects and arrays can be nested. Therefore, a file can follow JSON’s grammar and still exceed a particular parser’s limits. There is no universal threshold established here; check the target agent’s documentation if a large or deeply nested file parses elsewhere but fails when the agent loads it.
A safe way to diagnose the failure
- Validate the syntax. Use a JSON parser or validator, then correct the exact grammar errors it reports.
- Check the agent’s contract. Compare the root value, keys, nesting, and value types with the current configuration documentation or schema for your agent and version.
- Remove ambiguous object members. Make every key unique and avoid relying on key order.
- Investigate environment limits. If the document is valid and its structure matches the documentation, check for documented size or nesting limits, file encoding, and version-specific configuration changes. RFC 8259 requires UTF-8 when JSON is exchanged between systems outside a closed ecosystem.
- Parse safely. Do not execute file contents with
evalor a similar mechanism to read JSON. RFC 8259 warns that this creates an unacceptable security risk.
Why agent tooling does not imply one JSON format
Some agent-tooling protocols carry structured content or serialized JSON, but that does not define every agent’s configuration-file contract. For example, the Model Context Protocol’s server-tools specification dated 2026-07-28 says that a tool returning structured content should also return serialized JSON in a text-content block for backwards compatibility. That is a protocol behavior, not a universal configuration format. See the MCP server tools specification.
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