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

Annotations already declare readOnly/idempotent/non-destructive/open-world, so the safety profile is covered. The description adds genuinely new behavioral context: a 30-requests-per-minute rate limit and the failure mode that private/login-only content fails. It stops short of describing auth requirements or pagination, keeping it at a 4 rather than a 5.

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?

Three sentences, front-loaded with the core action, then the return payload, then routing to alternatives and the rate limit. Every sentence carries distinct information with no padding.

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?

With no output schema, the description compensates by enumerating the returned fields (platform, title, uploader, duration, heights, video/audio flags, gallery size, caption, hashtags, thumbnail). Combined with rate limits and failure modes, an agent has everything needed to call and interpret it.

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?

Only one parameter with 100% schema description coverage, so the schema already documents the URL, its example formats, and the private-post failure case. The description restates the platform set and failure condition but adds no syntax or format detail beyond the schema. Baseline 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?

Specific verb+resource ('Read the metadata of a public Instagram, YouTube, TikTok, X, Facebook or Pinterest post') with the explicit qualifier 'without downloading it'. It then enumerates the returned fields, so the agent knows exactly what this tool yields versus its siblings.

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?

Explicitly states when to use it ('use it first to check a link or pick a quality') and names the two alternatives with their selection conditions: download_media to get the file, transcribe_video for the spoken words. Nothing is left to inference.

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