fetch_posts

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

The readOnlyHint annotation already indicates a safe read operation. The description adds no additional behavioral details such as rate limits, pagination, or output format (though an output schema exists). With annotations present, the description provides minimal added value.

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 sentence that front-loads the core purpose. It is concise and contains no unnecessary 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?

Given that the input schema fully describes parameters and an output schema exists, the description is minimally adequate. However, it could provide more context on how listing_type and time_filter interact, but the schema descriptions partially cover this.

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 input schema has 100% description coverage for all 4 parameters, each with its own description. The tool description does not add meaning beyond what the schema provides, so a baseline score of 3 is appropriate.

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 'Fetch posts from a single subreddit', using a specific verb ('fetch') and resource ('posts') with a scope ('single subreddit'). This immediately distinguishes it from sibling tools like 'fetch_multiple', which implies fetching from multiple subreddits.

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 implicitly suggests usage for a single subreddit by specifying 'single', but it does not explicitly state when to use this tool versus alternatives like 'fetch_multiple' or provide any exclusions or context. With multiple sibling tools, clearer guidance would be beneficial.

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