fetch_json

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

With no annotations, the description carries the full burden. It discloses the core behavior (returns the JSON content as a string, honors max_length and start_index) but omits error handling, status codes, content-type validation, and header usage details. These are meaningful gaps for a network tool.

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 compact docstring with a summary line, Args list, and Returns line. Every sentence adds information, and the summary is front-loaded. No wasted words.

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?

It covers the essential invocation details: the required parameter, optional parameters, and return type. An agent can correctly call it using only this description. It falls short of 5 because it does not address error scenarios or explicitly relate the tool to siblings, but output schema and simple parameter set keep the gap small.

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 0%, and the description compensates fully by explaining all four parameters in the Args section, including defaults and the char-based meaning of max_length and start_index. Without this, an agent could not correctly invoke the tool with those options.

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 opening line 'Fetch a JSON file from a URL' uses a specific verb and resource, naming the exact content type. This clearly distinguishes it from siblings like fetch_html and fetch_markdown by the format it retrieves.

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?

The description gives a clear context: use this tool when you need to fetch JSON from a URL. It does not explicitly name alternative tools or exclusion criteria, so it is not a 5, but the intended use case is unmistakable.

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