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

Annotations already declare this is a non-read-only, non-destructive, closed-world mutation, so safety is covered. The description adds real behavioral context with the 'must already be signed in on the phone at the given slot' precondition, but it says nothing about duplicate-account handling, whether a phone rental must be active, or what happens on failure.

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?

Two sentences, front-loaded with the action and platforms, then the preconditions. Nothing is padding, though the platform/default and google_email clauses duplicate schema text and could have been trimmed.

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 five-parameter mutation with no output schema, the description covers prerequisites and platform rules but omits what the call returns (e.g. an account identifier) and how it relates to slot binding or existing accounts. Adequate but with clear gaps for an agent chaining calls.

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 the tiktok default, the TikTok slot requirement, and that google_email is YouTube-only and rejected elsewhere. The description restates these facts rather than adding new syntax or constraint detail, so 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 uses a specific verb and resource ('Link a posting account for the authenticated user') and names the three supported platforms, which is a much sharper statement than the title 'Create Account Tool'. It does not distinguish itself from the closely named sibling update-account-tool or delete-account-tool, but the create/link intent is unambiguous.

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 supplies a concrete precondition (the account must already be signed in on the phone at the given slot) and the per-platform default, which tells an agent when the call will succeed. It stops short of naming alternatives — e.g. that update-account-tool should be used when the account already exists — so there are no explicit exclusions.

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