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

Annotations already declare readOnly, idempotent, non-destructive, closed-world reads, so safety is covered. The description adds real value beyond that: the source database, the 'Story not found' failure return, and a warning to treat the user-generated content as untrusted input.

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 tight sentences, front-loaded with the core purpose, then usage source, then return/behavior details. Every sentence earns its place with no filler.

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?

Despite no output schema, the description enumerates the returned fields (taken_at, media_type, product_type, thumbnail_url, video_url, video_duration, user_pk), states the not-found case, and flags the untrusted-input nature. 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?

There is a single parameter with 100% schema description coverage, so the schema already documents story_id as the story pk. The description reinforces that the pk originates from get_user_stories but adds no format or validation detail beyond the schema, matching the baseline 3.

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 states a specific verb (Get), resource (one Instagram story), and key (by its ID/pk) from the DataLikers database. It clearly distinguishes itself from siblings like get_highlight_by_id and get_user_stories by scoping to a single story fetched by pk.

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?

It explicitly routes the agent: 'Use it for a story pk from `get_user_stories`', naming the sibling that supplies the required input. It gives clear context but stops short of any exclusion (e.g., when to prefer highlight or media siblings instead).

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