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

Annotations indicate idempotentHint=true and readOnlyHint=false, but the description adds substantial behavioral detail beyond annotations: the idempotent behavior (returning existing block on duplicate), the response returning the block AS STORED (so rejected fields are absent), and the phase field's dependency on campaign being set. This is exactly the kind of contextual behavior an agent needs to know and is not present in the structured metadata.

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?

The description is dense but well-structured: starts with the core purpose, then enumerates types, followed by required fields, then key behavioral notes. Each sentence carries information, and the structure front-loads the most critical aspects. It's appropriately detailed for a tool with 35 parameters and 18 types, though it could be slightly more scannable with bullet points, but it's not overly verbose.

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 complex tool with 35 parameters, nested objects, and an output schema, the description covers all critical aspects: types, required fields, URL validation, idempotency, phase semantics, and the campaign prerequisite. It even instructs the agent to check get_mini_site.campaign and inform the user if it's null. The output schema likely documents the return structure, so the description doesn't need to repeat that. It is complete for safe and correct invocation.

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 full burden of explaining parameters. It does so extensively: lists required fields per type, explains the phase enum, URL constraints, and the meaning of various fields like mode, links, etc. While not every one of the 35 parameters is individually explained, the description covers the most important ones and gives clear rules for required fields. It significantly compensates for the lack of schema descriptions.

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?

Clearly states 'Add one block to a bio page' with a specific verb and resource. Lists all 18 block types, distinguishing from siblings like remove_mini_site_block and update_mini_site_block by its add semantics. The description is unambiguous about what the tool does.

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?

Provides explicit per-type required fields, which is essential usage guidance. It also includes important behavioral notes like idempotency (calling twice returns existing block) and the phase field dependency on campaign. However, it doesn't explicitly contrast with update_mini_site_block or remove_mini_site_block, but the purpose is clear enough that an agent can infer when to add vs. update/remove.

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