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

Adds substantial context beyond the readOnly/openWorld annotations: the null-return case when metadata is absent, that such requests are not charged, the 1-credit cost, and the two source dialects carrying the count. These are exactly the behavioral details an agent needs before spending credits.

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?

Front-loads the purpose and usage guidance, then adds cost and failure-mode details. The parenthetical dialect names (edge_owner_to_timeline_media.count / media_count) are somewhat technical clutter but do explain the `source` field, which has no output schema to document it.

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 helpfully explains the null case, the credit cost, and what `source` conveys. The main omission is any guidance on cache_max_age, leaving an agent unsure how to use that second parameter.

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 schema documents 'handle' (accepts @handle or full URL) but leaves 'cache_max_age' unexplained at 50% coverage, and the description adds nothing about it. Baseline 3 is appropriate since half the parameters are covered by schema and the description does not compensate for the gap.

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 a specific verb+resource ('post count for a profile') and immediately scopes it against the fuller-profile sibling by saying 'Call this when a fuller profile is not needed.' An agent can distinguish it from instagram_profile without opening either schema.

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?

Gives an explicit selection condition ('when a fuller profile is not needed'), implying instagram_profile is the alternative for richer data. It stops short of naming that sibling directly or stating when this tool is the wrong choice, keeping it just below a 5.

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