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

With destructiveHint=true and idempotentHint=true already declared, the description adds the crucial substance: the write replaces that day's existing times rather than merging, which explains the destructive nature concretely. It also discloses the required 'Publish' permission and the auto-fill boundary via agentId, plus sets the correct mental model that no post is scheduled here.

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?

Roughly four short sentences, each carrying distinct information: purpose, replacement semantics, the cross-tool boundary, and the permission requirement. The destructive replacement caveat is front-loaded before the alternatives, which is the correct order for a mutating tool.

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 an 8-parameter mutating tool with full schema coverage and rich annotations, the description covers purpose, replacement risk, prerequisites, and siblings. The only gap is what a successful call returns or confirms (no output schema exists), which would help an agent verify the write—minor given everything else is covered.

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 every parameter including day, times, agentId, approval, isActive, timezone, and scheduleId is already documented in the schema; the baseline is 3. The description only reinforces the 'one weekday per call' constraint and the agentId empty-slot behavior that the schema already states, adding little new parameter-level meaning.

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 first sentence states a specific verb and resource with scope: 'Define the publishing times for one weekday.' It then explicitly distinguishes itself from the two nearest siblings: post_schedule_get (read first) and post_upsert with scheduledAt (per-post scheduling). An agent can route correctly without opening any 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?

It gives explicit when-to-use context and exclusions: one weekday per call, replaces rather than appends, read post_schedule_get first, and it does not schedule an individual post (use post_upsert with scheduledAt). The prerequisite ('Publish' permission on the plan) is also named, leaving nothing to inference.

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