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

Annotations cover safety (readOnlyHint=false, destructiveHint=false, idempotentHint=true), and the description adds real behavioral context beyond them: the response echoes the block 'AS STORED' so rejected fields are visibly absent, the concrete idempotency trigger, and the non-obvious rule that phase is a no-op until a dashboard campaign exists.

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?

It is long, but every clause is load-bearing given 35 parameters and zero schema descriptions. The core purpose is front-loaded, followed by the type/required-field reference, then the idempotency and phase caveats. No obvious filler sentences, though the type list and required-field block are dense to parse.

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?

An output schema exists, so return-value explanation is not required, yet the description usefully clarifies echo-as-stored semantics and the campaign prerequisite. It does not mention which parameter identifies the target site (siteId is not required in the schema), which for a 35-param tool is a small remaining gap.

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 0%, so the description carries the burden, and it does the highest-value work: it maps required fields per type (url, title+startDate, provider+url, timezone+days, embedUrl constraints, etc.) and the http(s) URL rule. Many optional params (order, limit, price shape, alt, caption, label, artworkUrl, visibleFrom/Until, postReleaseLinks) remain undocumented, so it compensates well but not completely.

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?

Opens with a specific verb+resource: 'Add one block to a bio page.' It then enumerates the block types, which immediately separates it from update_mini_site_block, remove_mini_site_block, and get_mini_site in the sibling list without the agent needing to open another 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?

Gives strong conditional guidance for the phase field (when 'before'/'after'/'always' apply) and an explicit prerequisite: check get_mini_site.campaign and warn the user if null. It also discloses the idempotency branch (same type+url returns existing block). It stops short of explicitly routing the agent to update_mini_site_block for existing blocks, so it is not a full when-not statement.

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