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Get issuing CA

get_ca

Read-onlyIdempotent

Return one issuing CA certificate by its SHA-256 fingerprint (the issuer_ca field of get_certificate): subject, issuer, validity, parent and cross-signed certificates, the number of certificates it issued and a page of them.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "sha256": "<sha256>"
    },
    "name": "get_ca"
  }
}

Input Schema

Name	Required	Description
`limit`	No	Issued certificates per call, 1 to 100; default 25
`cursor`	No	The next_cursor of the previous call, to get the next page; omit for the first page
`sha256`	Yes	SHA-256 fingerprint of the CA certificate, 64 hex characters

Output Schema

Name	Required	Description	Default
`issued`	Yes
`sha256`	Yes
`parents`	Yes
`related`	Yes
`has_more`	Yes
`issuer_dn`	Yes
`not_after`	Yes
`first_seen`	Yes
`not_before`	Yes
`serial_hex`	Yes
`subject_dn`	Yes
`next_cursor`	No
`self_signed`	Yes
`issued_count`	Yes
`pubkey_sha256`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 12, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is covered without description help. Beyond that, the description adds genuinely useful behavior: the result is paginated ("a page of them") and includes parent/cross-signed certificates and an issued-count, which is non-obvious structure an agent should anticipate.

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?

A single front-loaded sentence leads with the operation and key before the field enumeration. The trailing list of returned fields partially duplicates the output schema, which is mild redundancy, but nothing is padded or vague.

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?

For a three-parameter, read-only lookup with an output schema, the definition covers identification, provenance of the key, result shape and pagination. An agent has everything needed to select and invoke it correctly.

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

Parameters4/5

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, but the description adds meaning the schema does not: it identifies the sha256 parameter's provenance (the issuer_ca field of get_certificate) and frames the paging model around returned issued certificates rather than the CA record itself.

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?

The description states a specific verb and resource ("Return one issuing CA certificate") and pins down the exact identifier (SHA-256 fingerprint), plus enumerates the returned contents. It is clearly distinguishable from get_certificate, which returns the end-entity certificate that merely references this CA via its issuer_ca field.

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

Usage Guidelines4/5

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

It gives concrete entry guidance by naming where the fingerprint comes from (the issuer_ca field of get_certificate), which tells the agent how to chain from a leaf certificate to its issuer. It does not explicitly state exclusions or when a search tool like search_certificates would be preferable for an unknown fingerprint.

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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