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

Beyond the readOnlyHint annotation, the description discloses behavioral traits such as returning structured data, including a 'legacy format' section, and using a FastMCP context for progress reporting. It also details the exact data shape (engagement, audio, sections), which adds significant context about what the tool does and returns, going beyond annotation-only information.

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 clear headers for purpose, returned data, args, and return format. It is front-loaded with the primary purpose, and every line provides useful information without excessive prose. The bullet list and code block make it scannable and appropriately sized for a tool with this level of complexity.

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 description is complete for a read-only tool with this complexity. It explains the parameters, return structure, and even notes the legacy format. An output schema exists, but the description adds value by explaining the semantic meaning of fields like engagement and audio. There are no gaps that would leave an agent uncertain about how to invoke or interpret the tool.

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 zero descriptions for parameters, making the description's Args section essential. It explains post_url as 'Full Instagram post URL' and include_comments as 'Whether to include comments in the response'. It also documents the return structure in detail, fully compensating for the low schema coverage. The mention of ctx adds context about the FastMCP framework, providing additional meaning 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 'Get detailed post/reel information with structured data', specifying the verb (get), resource (post/reel), and scope (by URL). It lists specific data fields returned, distinguishing it from sibling tools like get_user_profile or get_user_posts, which target different resources (user-level vs. specific post).

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 implies usage by requiring a post_url and detailing the structured output, so the tool's purpose is clear. However, it does not explicitly state when to use this tool over alternatives or provide exclusion criteria. The context is clear but lacks explicit when/when-not guidance, so a 4 is appropriate.

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