capabilities-txt-registry
Server Details
Discover what websites across the agentic web can do — query the capabilities.txt registry.
- Status
- Healthy
- Last Tested
- Transport
- Streamable HTTP · MCP 2025-11-25
- URL
- Repository
- capabilityhostprotocol/capabilities-txt
- GitHub Stars
- 0
TDQS
Scored across 3 tools
Each tool has a clearly distinct purpose: searching capabilities, getting a site's capabilities, and listing all sites. No overlap in functionality.
All tool names follow a consistent verb_noun pattern with underscores: discover_capabilities, get_site, list_sites. The style is uniform and predictable.
Three tools is slightly low but appropriate for a read-only registry. The set covers the core operations: search, single lookup, and listing all entries.
The tool surface fully covers the apparent domain of querying the capabilities.txt registry. Includes search, site details, and site listing—no obvious gaps for read operations.
Available Tools
3 toolsdiscover_capabilitiesDiscover capabilities across the webAInspect
Search the capabilities.txt registry for sites that can do something — by capability id, keyword, or category. Returns matching capabilities with the site that offers them and its conformance grade. To invoke, fetch that site's /capabilities.txt.
| Name | Required | Description | Default |
|---|---|---|---|
| query | Yes | A capability id, verb, or keyword, e.g. "check_stock" or "refund" |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations provided, so description must fully disclose behavior. It describes return values but does not mention side effects (likely read-only), safety, or any limitations.
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 sentences, front-loaded with purpose, no redundancy. Every sentence adds value.
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?
Complete for a simple search tool, but could explain 'conformance grade' and any query limitations. Still sufficient given no output schema.
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% for the single parameter; description adds extra detail (category) beyond the schema description, enhancing clarity.
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?
Clearly states the tool searches a registry for sites by capability, keyword, or category, and distinguishes from sibling tools which deal with sites directly.
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?
Provides clear context on what to search and how to invoke after discovery, but lacks explicit when-not-to-use or comparison with siblings.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
get_siteGet a site's capabilitiesBInspect
Get the full list of capabilities a site declares, by domain.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | A domain, e.g. example.com |
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description does not disclose behavioral traits beyond the basic read operation. No information about authentication, error handling, rate limits, or data freshness is provided, and no annotations exist to compensate.
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 that conveys the purpose efficiently without extraneous 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?
Given the absence of annotations and output schema, the description lacks completeness. It does not describe the return format, edge cases, or additional context needed for effective use.
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?
With 100% schema coverage, the description adds minimal extra meaning. The phrase 'by domain' is already implied by the parameter description. 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 action (get), resource (list of capabilities of a site), and scope (by domain). It distinguishes from sibling tools like discover_capabilities and list_sites.
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. There is no mention of prerequisites, exclusions, or typical use cases.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
list_sitesList registry sitesAInspect
List every site that publishes a conformant capabilities.txt, with its grade and capability count.
| Name | Required | Description | Default |
|---|---|---|---|
No parameters | |||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries full burden. It states the output includes grade and count, but does not disclose any potential side effects, rate limits, or whether the list is paginated or sorted. For a read-only listing, this is adequate but not exhaustive.
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?
A single well-structured sentence that conveys all necessary information without redundancy. It is front-loaded and every word serves a purpose.
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 tool with no parameters and no output schema, the description covers the essential: what it lists and what information is provided. It might lack mention of ordering or limits, but given the tool's simplicity, it is reasonably complete.
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?
With zero parameters, the baseline is 4. The description adds value by specifying what the list contains (grade and count), which is not apparent from the empty 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 lists every site that publishes a conformant capabilities.txt, including grade and capability count. This distinguishes it from siblings like discover_capabilities (which likely discovers per site) and get_site (which gets a specific site).
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 use when you need a list of all qualifying sites with their grades and counts. It does not explicitly mention when not to use or name alternatives, but the context from sibling names clarifies boundaries.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Tool Schema Changelog
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
3 tool updates
- First observed
discover_capabilities - First observed
get_site - First observed
list_sites
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