fetch_json

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

No annotations are provided, so the description carries the full burden. It discloses key behavioral constraints: it is not a general web fetcher and refuses non-reddit URLs unless an env var is set. It implies read-only via 'Read', but does not explicitly state the return format (JSON) or mention rate limits/authentication. Even so, it covers the most important behavioral limit.

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 well-structured with a clear lead sentence, usage rules, and a limitation note. Each sentence earns its place, though it could be slightly tightened. Overall it is not overly verbose and reads efficiently.

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 single-parameter tool with no output schema, it covers the intended use cases, exclusions, and a critical behavioral limitation. It does not explicitly state that the returned data is JSON, but the tool name 'fetch_json' makes that obvious. The description provides enough context for an agent to invoke it correctly in the intended scenarios.

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 single 'url' param has no schema description. The description adds 'a reddit.com URL' and the main text provides examples of accepted shapes, partially compensating. However, the param-level description is redundant and not very detailed; an agent must rely on the overall description for semantics.

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 verb ('Read') and resource (Reddit feeds of user, multireddit, or domain types). It explicitly differentiates from siblings by saying 'the other tools do not cover' and lists concrete URL shapes, making the tool's niche immediately clear to an agent.

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?

Gives an explicit 'Use this only for' condition with URL shape examples, and names the exact alternative tools (browse_subreddit, search_reddit, get_post) for other cases. It also states when NOT to use it (not a general web fetcher), leaving little room for misrouting.

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