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

Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds real behavioral context beyond them: the result is per-account, the limit field is polymorphic (number vs the literal 'unlimited'), counts are monthly and reset, and a 'ready' flag signals missing Instagram messaging permission — meaningful since there is no output schema.

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?

A single dense sentence that front-loads the scope ('For each Instagram account') and then the three return fields. It is efficient with no wasted clauses, though the nested parenthetical about contacts_per_month is slightly hard to parse on first read.

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 zero-parameter read tool with no output schema, the description effectively substitutes for a return-value spec by naming each field and its semantics. Minor gaps remain: behavior when no Instagram accounts are connected, and whether usage is reported in a list keyed by account identifier, are left unstated.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The schema confirms an empty object and the description introduces no phantom inputs.

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 names a specific resource (automation messaging usage, per Instagram account) and enumerates the three returned facts (monthly messaged-contact count, plan limit as number or 'unlimited', reset timing), which clearly separates it from get_automation_insights or get_account_summary. It stops short of explicitly naming a sibling or stating 'this is a read-only usage report', so it is clear but not fully differentiated.

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?

There is no explicit when-to-use or when-not-to-use guidance, no mention of a prerequisite (Instagram account connected, messaging permission granted) beyond the incidental 'ready is false' note. The intended scenario — checking remaining monthly automation quota — is only implied by the content of the return values.

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