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

With no annotations, the description carries the full behavioral burden and does disclose two concrete traits: it costs 1 credit and requires a Bearer api_key authorization header. That is useful operational context, but it omits rate limits, error behavior, and whether the count reflects only public followers versus something else.

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?

Purpose is front-loaded in the first clause and the total length is short. There is minor noise (a doubled period after 'user id..') and semi-redundant metadata boilerplate, but no sentence is wasted.

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?

For a single-parameter read tool with no output schema or annotations, the description covers what it returns (a follower count), the credit cost, and the auth requirement. The absence of sibling differentiation detail is the main residual gap.

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 description coverage is 100%, so the sole user_id parameter is already fully documented (numeric Instagram user id sourced from User Info / Detailed Info). The description adds no format, sourcing, or edge-case detail beyond the schema, so the baseline 3 applies.

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 and resource ('Fetch the public follower count for a user id'), and the 'resource=followers' tagging along with the name makes it distinguishable from siblings like instagram_user or instagram_detailed. It clearly conveys scope (public follower count) without needing to open the 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?

No when-to-use or when-not-to-use guidance is given. The 'Platform=instagram resource=followers' line is metadata restatement, not a routing instruction, and no sibling tool is named as an alternative for related data.

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