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

Annotations already include readOnlyHint=true and idempotentHint=true, but the description adds specific constraints beyond those: 'SELECT statements only — writes, DDL, and file/HTTP table functions are rejected by the canvas gate.' It also mentions the workflow dependency on staging tools, which is valuable behavioral context not captured by annotations. The description does not contradict any annotation.

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 concise (about 4 sentences), front-loaded with the core purpose, and every sentence adds value: purpose, usage, example use cases, constraints, and prerequisite call. There is no fluff or repetition, making it efficient and well-structured.

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?

Given the tool is a SQL query against staged tables, the description covers all essential context: the staging mechanism (other tools), the required inputs (canvas_id and table_name), the workflow (call describe first), constraints (read-only, rejected functions), and example use cases. The presence of an output schema means detailed return values are not needed. This is complete for a tool of this complexity.

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 parameters (sql and canvas_id) are fully documented in the schema. The description reinforces their use but does not add new syntactic or semantic details beyond what the schema already provides (e.g., the schema already says 'Read-only SQL SELECT' and 'Canvas ID returned by gnomad_list_gene_variants or gnomad_search_clinvar'). Since the description adds no new parameter-level information, the baseline 3 is appropriate.

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 description clearly states what the tool does: 'Run a read-only SQL SELECT against a canvas table staged by gnomad_list_gene_variants (table gene_variants) or gnomad_search_clinvar (table clinvar_variants).' It specifies the verb (run), the resource (canvas table), and the scope (read-only SQL SELECT), and differentiates from siblings by naming the staging tools and the specific use cases (ranking, grouping, filtering).

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 provides explicit when-to-use guidance: 'Use the canvas_id and table_name those tools returned...' and 'Call gnomad_dataframe_describe first to discover staged table and column names.' It also gives explicit exclusions: 'writes, DDL, and file/HTTP table functions are rejected by the canvas gate.' This gives clear alternatives and context without ambiguity.

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