get_next_free_slot

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

Annotations already cover readOnly, idempotent and non-destructive, so the bar is lower; the description still adds real context by disclosing the data source (Settings posting times), the return type (ISO timestamp), and the empty-state behavior ('Says so plainly if no posting times are saved'). It does not describe the shape of that no-slots response or any timezone/rate-limit nuance.

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?

Three short sentences, front-loaded with what the tool returns, followed by the return format and the edge case. Nothing is redundant or padded.

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 the return-value burden and does so (ISO timestamp for scheduledFor) plus the no-posting-times case. For a single-parameter read tool with full annotation coverage, nothing an agent needs to call it correctly is missing.

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 single parameter is already documented in-schema with a pointer to list_connected_accounts. The description only restates 'one connected account' without adding format, scoping, or validation detail, 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?

States a specific verb and resource ('the account's next free posting time for one connected account') and scopes the source of truth ('from the posting times saved in Settings'). This is clearly distinguishable from sibling list_posting_slots, which enumerates slots rather than resolving the single next free one.

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?

The description embeds the intended use case by naming the consumer field ('Returns an ISO timestamp to use as scheduledFor'), which effectively routes the agent to call this before schedule_post/schedule_draft. It stops short of naming an explicit alternative or a when-not condition, so it is clear context without exclusions.

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