Identify a Reddit URL

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

Annotations already set readOnlyHint=true, indicating no side effects. The description adds valuable context: 'Costs 2 credits and parses offline without fetching the page' and returns INVALID_INPUT for non-Reddit URLs. No contradictions.

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 fairly concise and well-structured, with clear sentences. It could be slightly shorter, but every sentence adds useful information. Front-loaded with the core purpose.

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?

The tool has an output schema (not shown but flagged as true), so the description doesn't need to detail return values. However, it explains the output mapping and behavior adequately. With good annotations and a single parameter, the description is complete for agent use.

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 100% with a single parameter. The description enhances the schema by providing examples of valid URLs and explaining how the output maps to other tools (e.g., t3_ id for reddit_get_post). This adds significant value beyond the schema.

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's purpose: 'Identify what a Reddit URL points at before fetching it.' It specifies the output fields (type, id, handle, canonical_url) and distinguishes from sibling tools like reddit_get_subreddit by focusing on URL resolution.

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?

Explicit when-to-use: 'Give any reddit.com or redd.it URL.' Explicit when-not-to-use: 'Skip this tool when you already have a t3_/t1_ id, subreddit name, or username.' Also states it's not for non-Reddit URLs, providing clear boundaries.

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