Fetter MCP

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does not mention what the tool returns (e.g., boolean, vulnerability details), whether it makes network requests, or any error conditions. The description only restates the purpose and input constraint, leaving key behaviors undisclosed.

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 two sentences, with the primary action stated first and a supporting example second. Every word contributes value; there is no redundancy or unnecessary detail. This is a model of concise, front-loaded documentation.

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?

The tool is simple, with one parameter and no output schema. The description explains the purpose and input format well, but it does not explicitly state the return value or any edge-case behavior. Given the lack of an output schema, the description should clarify what the agent will receive, making it incomplete in that aspect.

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?

The schema description for the 'name' parameter is already very detailed, providing examples and specifying the exact format. The description adds minimal new meaning beyond reinforcing the 'exact version specifier' requirement, so it aligns with the schema and does not significantly enhance parameter understanding.

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 the action ('Check if') and the resource ('a specific package version'), and even specifies the required input format with an example. This distinguishes it from sibling tools like 'lookup' and 'most_recent_not_vulnerable' by focusing on a particular version's vulnerability status.

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 clear context for use: when you have an exact package version and need to know if it has known vulnerabilities. It also sets a prerequisite ('Requires an exact version specifier'), which guides the agent on valid inputs. However, it does not explicitly mention alternatives or when not to use this tool, leaving some ambiguity relative to sibling tools.

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

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

With no annotations provided, the description carries the full burden for behavioral disclosure. It mentions the basic lookup functionality but omits any side-effect information (though a lookup is likely read-only), default behavior, or handling of edge cases. The note about exact versions is in the schema but not in the description, so the description alone is under-informative.

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 a single, direct sentence with no redundant words or filler. It clearly conveys the core purpose without unnecessary detail, earning top marks for conciseness and structure.

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?

The description is adequate for a simple lookup but leaves gaps: it doesn't specify the return format (no output schema), the exact semantics of 'and/or', or how the tool behaves with exact version constraints. Given the tool's moderate complexity (4 parameters) and the presence of siblings, a bit more context would be helpful.

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 is 3. The description itself does not add parameter-level detail beyond the schema. The schema already provides rich descriptions for name, limit, cvss_filter, and retain_passing, so the tool's description need not repeat them.

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 uses a specific verb ('look up') and resource ('a package by name and optionally version'), and clearly states the outcome: finding available versions and/or vulnerabilities. This distinguishes it from sibling tools like is_vulnerable and most_recent_not_vulnerable, which are more targeted.

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 gives no guidance on when to use this tool versus the sibling tools (is_vulnerable, most_recent_not_vulnerable). It does not mention any prerequisites, exclusions, or alternative tools, leaving the agent to infer the appropriate context.

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

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

With no annotations provided, the description carries full responsibility for disclosing behavior. It only states the core action and does not reveal what happens when no non-vulnerable version exists, whether the return value is a version string or metadata, how version ordering is determined, or any assumptions about package registries. This lack of detail is a significant gap.

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 a single, well-focused sentence with no wasted words. It immediately conveys the tool's purpose without extraneous content.

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 simple one-parameter tool, the core purpose is clear, but the description lacks important operational details such as return format, error handling (e.g., if no safe version exists), and edge cases. Without an output schema or annotations, these gaps leave the agent with insufficient information for confident invocation in all scenarios.

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?

The input schema covers the only parameter 'name' with a clear description and examples (100% coverage). The tool description adds no extra semantics beyond the schema, so the baseline score of 3 applies, as the schema already does the heavy lifting.

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 the action ('Find') and the specific resource ('the most recent version of a package that has no known vulnerabilities'), which distinguishes it from sibling tools like 'is_vulnerable' (checks vulnerability status) and 'lookup' (general package lookup). It is not a tautology and conveys a precise purpose.

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 implies the use case (obtaining the latest safe version of a package) but provides no explicit guidance on when to choose this tool over siblings or when not to use it. There are no references to alternatives or exclusions, so usage context is only implied.

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