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

Beyond the annotations, the description discloses that this call may charge via MCP-native x402, distinguishes free vs. paid return behavior, documents retry-payment metadata in _meta['x402/payment'], and states that unsupported places return diagnostics rather than paid guesses. There is no contradiction with readOnlyHint=false; the charging side effect is consistent with a non-read-only operation.

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?

Every sentence adds operational value: invocation prerequisite, cost model, return behavior, exclusions, and installation command. The core instruction is front-loaded, and the paragraph is dense without being bloated.

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 dynamic executor whose behavior depends on an arbitrary selected catalog tool, the description covers the essential workflow, payment semantics, expected return categories, and fallback behavior. The absence of an output schema is mitigated by explicit free/paid return descriptions, and the schema plus sibling tool complete the picture.

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 the baseline applies: both 'name' and 'arguments' are already documented in the schema. The tool description itself adds no parameter-level detail beyond 'by name', so it neither elevates nor penalizes the score.

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 action ('Run one Locus catalog tool by name'), names the required precondition ('after locus_search_tools or a known tool name'), and clearly positions itself as the execution counterpart to the discovery sibling. This is not a tautology; it gives concrete meaning to the tool name.

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?

Explicitly says when to invoke this tool (after locus_search_tools or with a known tool name), contrasts free search/looking with paid execution, and lists forbidden use cases (web scrape, LinkedIn, generic fetch). This gives the agent clear routing guidance relative to the sibling tool.

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