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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds real value beyond that: per-call pricing ('1 credit per call'), the specific fields returned for details (caption, media URLs, engagement counts, timestamp, owner), and the accepted shortcode source. No behavioral contradiction with the annotations.

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 action-by-action structure with Actions/Inputs/Pricing lines is front-loaded and scannable, and every line carries information. It loses a little to redundancy, restating that action=details needs the shortcode in both action entries.

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?

Both enum actions are covered with required inputs, the chaining between them is explained, and pricing is disclosed. An output schema exists, so return values need not be spelled out, and the description's brief note about the details payload is a bonus rather than a gap-filler.

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% and the schema already states 'Required for: details/id' per parameter, so the baseline is 3. The description goes further by explaining where the shortcode comes from ('the part after /p/ or /reel/ in the URL, or from action=id'), which the schema only partially hints at with an example value.

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?

States specific verbs and resources per action: 'Get one Instagram post or reel in full' and 'Extract the shortcode from an Instagram post or reel URL'. An agent can tell exactly what each action produces. However, it never distinguishes itself from siblings like instagram_reels or instagram_search, so the boundary between this tool and those is left to inference.

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 gives useful internal routing: action=details needs a shortcode, and action=id produces that shortcode from a URL. That is implied workflow guidance rather than explicit when-to-use versus alternatives — there is no indication of when to prefer instagram_reels, instagram_search, or instagram_profile instead.

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