nslookup.io MCP Server

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

No annotations are provided, so the description carries the burden. 'Check' implies a read-only operation, and the description discloses what is returned, but it does not mention potential limitations, error scenarios, or any permissions/rate limits. This is adequate but not rich.

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 sentence, front-loaded with the action, and lists return values efficiently. No redundant or filler 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 single-parameter tool with no output schema, the description is fairly complete. It names the specific return items (DNS status, VMC details, logo URL, trademark info, expiry) and the input domain. Minor gaps like error handling or prerequisites are not critical here.

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 coverage is 100% with a descriptive 'domain' parameter. The description repeats 'domain' but adds no extra parameter semantics beyond what the schema already provides. 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?

The description clearly states the tool 'Check BIMI and VMC for a domain' with specific verb and resource, and lists return values. However, it does not explicitly distinguish itself from sibling tool 'bimi_check' or other DNS/SSL tools, so it lacks sibling differentiation.

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?

No guidance is provided on when to use this tool versus alternatives like 'bimi_check' or 'ssl_certificate'. The description only states what it does, not context or exclusions.

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, the description carries the full burden. It clearly indicates a read-only lookup operation and mentions the DNS server context, but it does not disclose potential errors, timeouts, or the response format. The behavior is straightforward, yet lacks depth for a fully transparent picture.

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 long, front-loads the purpose, and lists the record types efficiently. Every word earns its place with no redundancy or fluff.

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?

Without an output schema, the description should explain the structure of returned results, but it only says 'returns results' without specifying format or shape. The tool has only two parameters and no side effects, yet the missing return details leave a notable gap for the agent.

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 provides 100% coverage with descriptions for both 'domain' and 'server', including an enum and a default value. The tool description adds minimal semantic value beyond what the schema already states, so the baseline of 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 uses a specific verb ('look up') and a resource ('all common DNS records') with a clear list of record types, which distinguishes it from sibling tools like dns_health or dns_propagation. It also specifies that results come from a designated DNS server, fully clarifying the tool's scope.

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 general usability for comprehensive DNS lookups but does not explicitly state when to use this tool versus alternatives like dns_record or dns_propagation. No exclusions or conditional guidance are provided, leaving the agent to infer the tool's place among siblings.

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, the description carries the full burden. It reveals the tool's scope (18+ servers) and outcome (shows propagation worldwide), but does not disclose behavior such as whether it is read-only, rate limits, or error handling. The read-only nature is implied but not explicit.

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?

Two sentences, front-loaded with the main verb and purpose, with no unnecessary words. It is concise 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?

For a simple 2-parameter tool with no output schema, the description is fairly complete: it explains what it checks, the scope, and the expected insight. It could mention how results are presented, but is adequate for a basic query tool.

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 schema already explains both parameters well. The description adds context about the global server coverage but does not introduce new semantic details beyond the schema.

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 states a specific verb ('check') and resource ('DNS propagation for a domain'), with clear scope ('across 18+ global DNS servers'). It also differentiates from sibling tools by emphasizing worldwide propagation status rather than a simple lookup or health check.

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 its use case: verifying if DNS changes have propagated globally. It provides context but does not explicitly mention when to prefer it over alternatives like dns_lookup or dns_health, nor any exclusions.

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?

No annotations are provided, so the description carries the full burden. It only states that the tool 'looks up' records and supports many types, but does not disclose network behavior, read-only nature, rate limits, or any side effects. This leaves the agent without important behavioral context.

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 sentence with a clear purpose and a list of supported types. It is concise and front-loaded, with no redundant words or filler.

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 relatively simple, and the schema covers all parameters. However, there is no output schema and no description of the return format, error behavior, or how to interpret results. An agent would benefit from knowing what the response contains.

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 adds no extra parameter semantics beyond the schema; it merely repeats record types already in the enum. The server parameter is not mentioned in the description at all.

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 tool's function: 'Look up a specific DNS record type for a domain.' It specifies the verb (look up), resource (DNS record type), and scope (for a domain). It also lists many supported record types, distinguishing it from broader DNS tools like dns_lookup.

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 usage is implied: use this tool when you need a specific DNS record type. However, there is no explicit guidance on when to use this instead of sibling tools like dns_lookup or dns_health, and no exclusions are mentioned.

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, the description carries full burden. It discloses the outputs (findings with severity levels) and the scan scope, which is informative. It doesn't mention potential side effects or authentication needs, but for a scan tool this is less critical.

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?

Two sentences, front-loaded with action, no fluff. It earns its place and is easy to parse.

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 with no output schema, the description covers purpose, scope, and return format. It lacks details on any prerequisites or limitations, but these are minimal for this kind of tool.

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 fully documents the single domain parameter, so baseline is 3. The description confirms the domain input but doesn't add syntax or additional constraints beyond the schema.

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 tool runs a security scan on a domain and lists specific checks (DNS misconfigurations, SPF/DKIM/DMARC, cookie security, web vulnerabilities). This distinguishes it from siblings like dns_health or ssl_certificate by covering a broader security posture.

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 when to use (when you need a security scan for a domain) but doesn't explicitly compare with sibling tools or specify when not to use. It provides clear context but no exclusions.

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, the description carries the full burden. It lists output fields, which reveals the tool's read-type behavior, but it does not explicitly state that it is non-destructive, makes network requests, or any other side effects. There is no contradiction with annotations, but the description omits safety assurances.

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-structured sentence that leads with the action and then lists key return fields. It is concise and information-dense with no wasted words.

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 compensates by enumerating the returned data (issuer, expiry, chain validity, etc.). This provides useful context, though it omits potential error scenarios or network behavior.

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 already fully documents the single 'domain' parameter with an example. The description adds little beyond the schema, listing return values but not giving extra detail about the parameter itself, so 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 the tool's function as checking SSL/TLS certificates for a domain and enumerates the specific data returned, distinguishing it from broader tools like security_scan, but it does not explicitly reference sibling tools. This gives clear purpose but lacks explicit differentiation.

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?

No guidance is provided about when to use this tool versus alternatives such as my_certificates or security_scan. The description simply states what it does without any contextual or exclusionary instructions.

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 of behavioral disclosure. It describes the tool as a 'one-time' check (not continuous monitoring) and specifies the return data (status, code, response time), but does not mention error handling, rate limits, authentication needs, or network constraints. This covers core functionality but leaves gaps in operational details.

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, efficient sentence that front-loads the purpose and key return values without unnecessary words. Every element ('one-time HTTP uptime check', 'URL', 'returns...') serves a clear purpose, making it easy to parse and understand quickly.

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's moderate complexity (HTTP check with timing), no annotations, and no output schema, the description provides a solid foundation but lacks details on error responses, retry behavior, or output structure. It is complete enough for basic use but would benefit from more context on failure modes or performance characteristics.

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%, with both parameters ('url' and 'timeout') well-documented in the schema. The description does not add any parameter-specific details beyond what the schema provides, such as URL format examples or timeout implications. Baseline score of 3 is appropriate as the schema handles parameter documentation adequately.

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 specific action ('perform a one-time HTTP uptime check'), the resource ('on a URL'), and the outcome ('returns whether the site is up or down, HTTP status code, and response time'). It distinguishes itself from sibling tools like 'security_scan' or 'ssl_certificate' by focusing solely on uptime monitoring rather than security or certificate analysis.

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 usage for checking website availability with timing metrics, but does not explicitly state when to use this tool versus alternatives like 'security_scan' for vulnerability checks or 'dns_lookup' for DNS issues. It provides basic context but lacks explicit guidance on exclusions or prerequisites.

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?

No annotations are present, so the description carries the full burden of behavioral disclosure. It accurately describes the primary behavior (A/AAAA lookup and domain representations) but omits potential edge cases like DNS errors, timeouts, or validation of invalid domains.

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 concise sentences with no fluff. The primary function is front-loaded, and the additional detail about punycode/unicode representations is placed second.

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 simple nature of the tool and the schema fully documenting the parameter, the description covers the core functionality well. It could mention potential limitations (e.g., live vs cached data) but is reasonably complete for a DNS lookup tool.

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 provides 100% coverage for the single 'domain' parameter, including an example. The description adds no additional semantic information beyond what is already in the schema, so the baseline of 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 the tool retrieves IPv4 and IPv6 addresses via A and AAAA records for a given domain, and also returns punycode/unicode representations. This specific verb+resource combination distinguishes it from broader sibling tools like dns_lookup.

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 usage when IP addresses are needed, but does not explicitly mention when to prefer this over DNS-related sibling tools like dns_lookup or dns_record. No alternatives or exclusions are provided.

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