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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds meaningful context beyond that: 'The sequence LEAVES THE MACHINE' makes the external egress and data-disclosure consequence explicit, and it names the downstream artifacts (hits, tabular report, job id). It still omits anything on service limits, queuing, or how long remotely-run jobs take.

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?

Three lean sentences with the purpose front-loaded, then the variant scope, then the downstream payoff, closing on the all-caps network warning. No padding or restated boilerplate; every clause carries information.

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 structure need not be re-explained, and annotations cover the read-only/open-world safety profile. The description supplies purpose, egress behavior and downstream artifacts, which is sufficient for a tool this complex with nested objects and 9 parameters. Missing only explicit sibling routing for the many other BLAST-like tools.

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% and every parameter (email, region, feature, program, sequence, databases, parameters, plus the nested _subject/_files) carries its own documentation, so the schema does the heavy lifting. The description restates the program list but adds no syntax, format, or default meaning beyond what the schema already provides, so the baseline of 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 and resource ('Search a sequence against NCBI BLAST+ at EMBL-EBI'), enumerates the programs and databases covered, and describes the transformation ('turns an unnamed span into named homologues with E-values'). It is unambiguous what the tool does, but it never differentiates itself from blast-like siblings such as blast_project_sequences, delta_blast_smart, rps_blast_cdd, or ebi_align.

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?

Use is implied rather than directed: 'This is the similarity search a methods section cites' positions it as the canonical homolog search, and the note about handing the job id downstream hints at workflow placement. There is no explicit when-to-use/when-not guidance and no named alternative for more targeted BLAST variants in the sibling list.

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