Taproot: AT Protocol MCP

search_lexicons

Read-only

Browse or search the registry of published AT Protocol lexicon schemas. The response's total field is the exact registry size and matched is the exact match count. Substring matches the NSID or description (query 'profile' → anything containing 'profile'); prefix the query with a DOT for a suffix match (query '.profile' → only NSIDs ENDING in .profile, i.e. profile record types). Filter by schema kind with type — 'give me every space lexicon' is type='space' with NO query, since an NSID does not imply its type (space.saebyeok.permissionSet is a permission set; app.kimbia.circle is a space). Types: the spec's primary types are record, query, procedure, subscription, and permission-set; a main def may also be a non-primary type (object, token, string); space comes from proposal 0016 (permissioned data), which is not in the ratified spec; defs-only marks a schema file with no main definition. Every response carries a typeCounts breakdown of the returned matches (it sums to matched), so one call with no arguments shows which kinds exist and how many; when you filter by type, otherTypes reports what the filter excluded, so a too-narrow or misspelled type still shows you the real options. Without a query or type, returns the total plus a sample. Results are paginated by limit; to see matches beyond the first page, call again with the offset printed at the end of the list. Use resolve_lexicon for a specific schema's full definition.

Input Schema

TableJSON Schema

Name	Required	Description
`type`	No	Keep only these schema kinds, e.g. "space" for permissioned space declarations, or ["record","procedure"]. Case-insensitive. Combine with query to search within a kind.
`limit`	No	Page size (1-100, default 50). A cursor in the response means more pages exist.
`query`	No	Optional substring to filter by, e.g. "profile" or "app.bsky".
`offset`	No	Skip this many matches (pagination). Use the offset value printed after a truncated list.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 13, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Annotations already mark it as read-only and open-world, but the description adds crucial behavioral context: exact semantics of total vs matched, pagination via offset and limit, typeCounts returning a breakdown of matches, and otherTypes reporting excluded kinds. This is far beyond what annotations provide.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is dense but well-structured, with each sentence adding concrete information. It is longer than average but avoids fluff, front-loading the core purpose and then elaborating on behavior, which is appropriate for a search tool with nuanced semantics.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of the registry (multiple schema kinds, non-obvious type relationships, pagination), the description covers all necessary context for correct invocation: how to interpret total and matched, how to handle types, pagination, and when to use the sibling resolve_lexicon. An output schema exists, but the description still adds useful semantic detail about response fields.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the schema already documents all four parameters. The description adds value by explaining that type does not imply query, showing examples like space.saebyeok.permissionSet, and clarifying substring matches and dot-prefix suffix matching for query. However, the schema already covers most of this, so a baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource: 'Browse or search the registry of published AT Protocol lexicon schemas.' This clearly distinguishes it from sibling resolve_lexicon, which the description itself names as the alternative for a specific schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly says to use resolve_lexicon for a specific schema's full definition, and gives conditions for each mode: with query, type filter, or neither. It even handles the edge case of type-only searches and misspelled types.

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

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