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

Annotations already establish this is a non-destructive, closed-world read, so the bar is lower; the description still adds substance by disclosing that parsing uses WUSS notation and that the tool also produces a support measure of how well the aligned rows back the consensus. It does not mention failure modes for malformed or empty `#=GC` lines, but the core behavior beyond annotations is well conveyed.

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?

One sentence, front-loaded with the primary read action and followed by the secondary measurement. The stacked parentheticals (WUSS, Rfam/Infernal) are informative but make it denser than necessary; nothing is outright wasted.

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 values need no explanation, and the nested `_subject`/`_files` structure is fully documented in the schema. The description covers the domain-specific prerequisites (Stockholm source, WUSS consensus line) and the dual purpose, leaving nothing an agent needs to call it correctly.

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 all three parameters are already documented, including the Stockholm-only constraint on `text`. The description restates the format expectation but adds no syntax or handling detail beyond the schema, so the baseline 3 applies.

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?

States a specific verb pair (read + measure) against a precisely named resource: the `#=GC SS_cons` line of a Stockholm alignment in WUSS notation. That level of specificity cleanly separates it from sibling tools like read_structure, fold_rna, and alignment_agreement without needing to name them.

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?

Usage is only implied: the description says the tool reads what a Stockholm alignment states, which hints the input must be a Stockholm alignment, and warns that WUSS is what Rfam/Infernal write. The explicit exclusion (CLUSTAL/PHYLIP refused by name) lives in the schema, not the description, and no alternative tool is named for when an agent lacks a consensus line.

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