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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false, so the safety profile is covered by structured data. The description's added value is the ordering constraint "Preview first," which is genuine behavioral context. It says nothing about failure modes, block ordering, or whether repeated calls stack duplicate blocks, which matters given idempotentHint=false.

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?

Two short sentences, zero filler, with the mutation stated before the prerequisite. The telegraphic "Preview first" fragment is efficient but slightly under-specified, which keeps it from a 5.

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 non-idempotent mutation with no output schema, the definition covers the action and the preview prerequisite but omits what the call returns (e.g., a block ID) and where the config's "listed fields" come from, presumably report_describe_fields. Adequate but leaves real gaps for an agent building a dashboard programmatically.

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 both dashboardId and config are documented in the schema, making 3 the baseline. The description only reinforces the single-block granularity of config; it adds no detail on the config payload, and the schema's own "using listed fields" pointer is left unexplained.

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?

"Add one block to a dashboard" gives a specific verb (add) plus resource (block) plus scope (one, to a dashboard), which is enough to distinguish it from report_update_block and report_remove_block. It stops short of naming those siblings explicitly, so differentiation is inferred from the name rather than stated.

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?

"Preview first" is a real usage directive that implies report_preview_block should be called before this tool, but the sibling is never named and no condition or exclusion is given. The agent must map the phrase onto the sibling list itself.

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