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

Goes well beyond the read-only annotations: discloses Threads snapshot behavior, null vs. zero semantics (absent data, missing permission, pending approval), possible cached values, and the unsupported Company account case. This is exactly the extra context an agent needs before relying on the numbers.

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?

Four tight sentences with no filler; the core resource and the Threads caveat are front-loaded. Density is high but every clause carries information.

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 carries return-value semantics itself and does so well: it explains null, zero, unavailability, and caching. Combined with access prerequisites, an agent has everything needed to call and interpret this tool.

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%, with platform enum and platformId pointing to list_connections already documented in the schema. The description adds platform-level behavioral nuance but no new meaning about how to supply platformId (prefix optional is only in the schema).

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 the specific resource ('profile counters') and enumerates the supported platforms, and the body clarifies which counters (followers, following, post count). It is distinguishable from post_stats by scope, though it never names that sibling explicitly.

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?

Provides useful preconditions (personal analytics access, platform availability checks, Company accounts unsupported) and platform-specific limits for Threads. However, it never says when to prefer this over siblings like post_stats or account_context, leaving the routing decision implicit.

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